For thousands of asylum seekers, there are many ways to wait — and wait, and wait — at the threshold of the United States.

Parents and children sleep in tents next to bridges leading to Texas for weeks on end, desperately hoping their names and numbers are called so they can be let in.

Some immigrants complain of shakedowns and kidnappings by gangs and corrupt officials, particularly across the border in Texas. Others have paid to jump to the front of the line; the rest, determined to enter the country legally, wait patiently, even if it takes months.

This is what has happened since the Trump administration placed asylum in a chokehold.

The Associated Press visited eight cities along the U.S.-Mexico border and found 13,000 immigrants on waiting lists to get into the country — exposed to haphazard and often-dubious arrangements that vary sharply.

Cuban migrants are escorted by Mexican immigration officials as they cross the Paso del Norte International bridge to be processed as asylum seekers on the U.S. side of the border. (AP Photo/Christian Torres)

The lines began to swell in the last year when the administration limited the number of asylum cases it accepts each day at the main border crossings, leaving it to Mexican agencies, volunteers, nonprofit organizations and immigrants themselves to manage the lines.

Central American families have reached the border in growing numbers since October, creating what is widely considered a humanitarian crisis.

In some cities, days pass without anyone being processed, the AP found. In San Diego, up to 80 are handled each day, but the line in Tijuana, across the border, is the longest anywhere — about 4,800 people.

Each day at each crossing, U.S. Customs and Border Protection officials alert Mexican counterparts how many people they will take — a system that U.S. authorities call metering. Then the keeper of the list lets immigrants know who can go into the U.S. for asylum interviews.

It is impossible to predict how many. Migrants pick their route based on a best guess of which city will offer the fastest crossing, and which will offer the safest stay in the meantime.

A federal lawsuit says the administration is violating U.S. and international law by refusing to take asylum seekers when they show up at a crossing, even temporarily. U.S. authorities argue that processing capacity dictates how many people it can handle.

"It's not turning people away, it's asking them to wait," then-Customs and Border Protection Commissioner and current acting Homeland Security Secretary Kevin McAleenan said in October.

But some feel they cannot. They try to enter illegally, sometimes with tragic consequences.

A Honduran family, arriving at Piedras Negras, Mexico, decided the line was too long. Crossing the Rio Grande, they were swept away; a father and three children, including a baby, are believed to have died.

CIUDAD JUAREZ: Black ink, wristbands, and thousands in line

A government employee emerges from an office building around 9 a.m. and stands atop a short stairway. A large group of Cubans push forward, eager to learn about their progress in line. "Move back, move back!" she says.

Another official shouts the numbers of asylum seekers at the top of the list.

"7,449!" he yells, and a man steps forward with identification to join 19 others who will be escorted across a bridge to El Paso, Texas.

Ciudad Juarez from Dario Lopez on Vimeo.

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Migrants in Juarez, Mexico, wait to hear their number called. (AP Video)

The sprawling industrial city began its waiting list in October when many Cuban asylum seekers began sleeping on the narrow sidewalk of a busy international bridge. Mexican authorities decided they had to go.

Casa del Migrante, the city's largest migrant shelter, is located about a half-hour drive from the bridge. It began registering asylum seekers and writing numbers on their arms with black ink. After widespread criticism, migrants were given numbers on plastic wristbands instead.

Some sold wristbands to people eager to skip the line or gave them to others when they decided to cross illegally, said Enrique Valenzuela, executive secretary of Chihuahua state's Migrant Services Center. Others made fake bracelets to cut in line. Arguments would erupt when two people showed up with the same number.

"Opportunists made a business out of it," he said. "It was easy to make money from it."

In late March, the state government took over from the shelter, taking custody of four notebooks with handwritten names paired with numbers, up to No. 10,221. Names and photos are now entered into a computer; the government created a closed Facebook group that is updated twice a day, so asylum seekers can check how many people the U.S. will take that day.

There are currently about 4,500 names on the list.

REYNOSA: 'River owners' run the show

The challenges faced by asylum seekers waiting in Reynosa, across from McAllen, Texas, are compounded by rampant violence.

There were 1,472 murders recorded last year in the state of Tamaulipas, where Reynosa is located. Gunfights between cartels and police occur daily, and the U.S. State Department has warned Americans not to travel there. Few Americans are willing to visit the shelter that maintains the list of asylum seekers, or the other churches and hotels where asylum seekers wait.

Jose Alfredo Diaz Reyes, 60, of Honduras, shows scarring on his lower back that he says is from an attack by suspected gang members in his native country while waiting at the Senda de Vida shelter in Reynosa, Mexico, May 1, 2019. (AP Photo/Eric Gay)

Jennifer Harbury, a longtime human rights advocate based in Texas, spoke recently to a large group of asylum seekers at the Senda de Vida shelter and met with people who had been kidnapped by cartels.

"The owners of the river, you know who they are," Harbury said. Several nodded.

Rather than stopping the cartels, Harbury alleges, some Mexican government officials shake down migrants. She said she's spoken to two people who were detained in the basement of a Mexican government office by security who demanded ransom payments to release them.

One woman from Central America told the AP that she and her two children had been smuggled from southern Mexico to the Rio Grande for $3,000. But when they arrived in Reynosa, she says, the coyote demanded $1,000 more.

She was held with her 2-year-old son in one room of a house, and her 4-year-old son was detained in another. The smuggler released them after six days after she didn't produce the extra money and left them at the international bridge. They were told to say they had been robbed and had nowhere to go.

A man on the street gave her a few pesos for a taxi to Senda de Vida. She and her children now wait with hundreds of others, some of whom have been there since January.

"I'm still afraid," said the woman, who spoke on condition of anonymity because she fears retribution from the smugglers. "I'm afraid they will see me, they will recognize me, and they will grab me."

Reynosa's list, handled by shelter director Hector Silva, has 370 people. Standing next to Harbury, Silva told asylum seekers that he wanted Senda de Vida to be a refuge from the organized crime and bribery outside its white concrete walls.

"There is no corruption in this house," he said.

PIEDRAS NEGRAS, MEXICO: The WhatsApp List

When asylum seekers arrive at the Frontera Digna migrant shelter in Piedras Negras, they are given a phone number to text on the messaging service WhatsApp. They're supposed to send the names and photos of everyone in their group. Then they're told to wait.

Managing the list is a local restaurateur named Hector Menchaca, who also serves as the local government's liaison to U.S. Customs and Border Protection.

Sitting in the dark lobby of his Piedras Negras steakhouse, Menchaca said U.S. officials call him daily to tell him how many people they would accept at one of the bridges heading to Eagle Pass, Texas. He then sees who's at the top of the list and sends them a WhatsApp message.

About 360 people are on the list, with another 200 people waiting to join it because the government has closed it to new entrants for the time being, Menchaca said.

"I tell everyone: Live with your telephone. Keep it in your hand," he said. "If I call you and you don't answer, I'm not going to search for where you are."

A father waits with his daughter and son in Piedras Negras, Mexico, as they seek asylum in the U.S., March 27, 2019. (AP Photo/Nomaan Merchant)

The list includes people from Central America, Mexico, Brazil, and countries an ocean away like Cameroon. They aren't told how close to the top they are, only that they might wait for two or three months.

Bernardo Blanco Romero said he left Mexico's southern state of Guerrero because of drug cartel violence and a lack of jobs and chose to go Piedras Negras because it is considered safer than other cities on the border.

"I'm going to wait; I have no other option. I don't have money to return," he said. With him were his wife and four children.

Obed Cuellar, a subdirector at the shelter, said a typical family stays two nights and three days before having to seek lodging elsewhere. Churches across the city have opened shelters, and advocates rely on a loose network of boarding houses.

But many people say they can't wait — among them the four who are believed to have drowned in the Rio Grande last week. Cuellar said he met the father weeks earlier when he and his family were at the shelter and decided to cross the river. Cuellar tried to persuade the family not to go.

"He said, 'God will help me to cross the river with the kids,'" he said.

The Border Patrol later rescued four people from the river, including two children, and recovered the body of a baby. The missing father and two children have not been found and are presumed dead.

NOGALES: A family affair

Ninoska Marisol Martinez Ortiz cradles her 15-month-old baby in her arms, occasionally wiping the child's runny nose, as she describes the time she has spent in Nogales. She had spent 45 days on the Mexican border town's wait list, which has about 1,000 names on it.

She was among several dozen immigrants, mostly from Central America and Mexico, who gathered at a chapel adorned with images of Our Lady of Guadalupe.

"How many people have been here 30 days?" a reporter asks. About half of the hands go up.

Sheyla Matamoros has been there 48 days. Carlos Quintero doesn't know how long his wait has been.

Brenda Nieblas, whose family manages another local shelter, keeps the list of new arrivals.

Before she was involved, Nieblas says hundreds of migrants would wait at the border crossing and many would try to rush in when U.S. authorities called people for processing.

Nogales from Dario Lopez on Vimeo.

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A reporter asks asylum seekers in Nogales, Mexico, whether they've been waiting at a shelter for more than 30 days. (AP Video)

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A reporter asks asylum seekers in Nogales, Mexico, whether they've been waiting at a shelter for more than 30 days. (AP Video)

Now, she keeps track of names and assigns numbers. Most days, only a few migrants are admitted. Some days, no one gets in.

When they first arrive, some of the migrants are sent to a Red Cross first aid station — like the mother whose 3-year-old wouldn't stop crying. A medical staffer found no infection but said she was dehydrated from the journey north.

They are then connected with Nieblas, who puts them on the list, assigns them to a shelter in Nogales and notifies them when their time comes.

SAN LUIS RIO COLORADO: 'There really is no schedule'

Darwin Mora manages two giant white boards with hundreds of numbers in black marker, each one representing a family or single adult. When CBP tells Mexican authorities how many people it wants, it falls to Mora to have them ready. Each family that crosses or cancels is marked with an X.

Mora, a towering figure and fast talker who prides himself on attention to detail, says CBP can call any day from 8 a.m. to 10 p.m. During those hours, he never strays far from the boards under a green canopy, which are divided in neat columns and rows. In the lower left corner of each box is a number to represent the number of people in the family.

"There really is no schedule," he said. "It would be so good if we had a fixed schedule but, in reality, it could be at 7 at night, 3 in the afternoon. There is no regular number. 'Hey, I need a group of two. I need a group of five.' Nothing is the same."

Darwin Mora, an asylum seeker from Venezuela, manages a list of people waiting to claim asylum in the U.S., May 5, 2019. (AP Photo/Elliot Spagat)

After a large encampment of asylum seekers was shut down earlier this year — with more than 200 families lined up under tarps on a strip of dirt and breathing exhaust fumes from cars — Mora enforces a new rule that limits camping on the border to six tarps and 15 families. Those slots are for families about to be called, allowing them to be ready on a moment's notice.

There are about 900 people on the list, assuming three people per family. Recent arrivals are expected to wait at least five months.

Isabel Mola, 29, fled an abusive marriage in central Mexico two months ago with her three sons, ages 8, 5 and 1. A friend told her San Luis Rio Colorado was safe and the waits to cross the border were tolerable. She is No. 306 on the white board and doesn't know how long she will be there.

"Some days they take people, then they don't, then it's every third day," she said after preparing a large pot of vegetable soup for at the migrant shelter for women and children where she stays.

Migrants walk between tents, left, and cars waiting to cross the border in San Luis Rio Colorado, Mexico and Arizona, May 5, 2019. (AP Photo/Elliot Spagat)

Mora knows his ownership of the list is temporary. The Venezuelan immigrant is waiting with his wife and two sons and hopes to settle with family in Phoenix after claiming asylum.

Mora is training a Mexican asylum seeker to manage the list when his number, 181, is called.

"When the time comes for me to cross, he knows everything," Mora said of his successor. "I have total faith in him. You have to pick the right replacement because the list is a big, big, big responsibility."

TIJUANA and MEXICALI: A notebook, and waiting for the phone call

Tijuana is most experienced with a numbering system, having established one in 2016 when Haitians had to wait in Mexico for a chance at refuge in the United States. Its waiting list stands at about 4,800.

Grupos Beta, a unit of Mexico's immigration agency that provides food, transportation and aid to migrants, keeps guard at night over tattered notebooks and hands them over to volunteers during the day to register new arrivals. On a recent Saturday, there were nearly 100 people in line to get a spot in the notebook — almost exclusively Cameroonians who arrived the previous day.

A volunteer with a bullhorn then ran through 110 numbers to fill 70 slots to cross that day.

The back of a girl from the Mexican state of Michoacan displays a name and number, written in ink. She waits to apply for asylum in the United States with her mom and sister, in Tijuana, Mexico, April 25, 2019. Her mother said she wrote the informat… — The back of a girl from the Mexican state of Michoacan displays a name and number, written in ink. She waits to apply for asylum in the United States with her mom and sister, in Tijuana, Mexico, April 25, 2019. Her mother said she wrote the information on her daughter because she feared losing track of the child if separated during the asylum application process. (AP Photo/Gregory Bull)

In nearby Mexicali, Grupos Beta employees in bright orange shirts call out those whose numbers are up. Mexicali — a city of about 1 million across from Calexico, California — has about 800 names on its list.

Two migrant shelter managers said they get a day's notice of the next numbers to be called, but Heidy Lainez and her 3-year-old son, Gonzalo, got only a half-hour warning that their slots — 2,155 and 2,166 — were up. She had waited a month.

"You have to have your suitcase packed," said Lainez, 29, of Honduras. "If you're not ready, you lose your turn. You always have to have your telephone in reach."

MATAMOROS: A long wait and 'no space' for families

At the foot of the bridge connecting Matamoros, Mexico, to Brownsville, Texas, more than 20 sheets of paper have been taped to a large board with the typewritten names of more than 800 people. The migrants waiting in Matamoros check the board daily to see whose names have been crossed off with a black marker.

Some of the names have a line next to them with the word "rio," Spanish for river, denoting that they were believed to have crossed the Rio Grande to enter the U.S. without authorization.

Around 50 people can sleep in tents closest to the bridge if they are at the top of the list. The rest stay in nearby hotels, boarding rooms, or shelters.

Many who had questions about the list relied on Cynthia Mayrena, a 29-year-old woman from Nicaragua who had been on the list since January with her husband and 4-year-old son. She said she sees single adults and teenagers pass through far more quickly than families.

"Sometimes 20 days go by without a single one passing," she said. "They say there's no space there for families."

There are frequent allegations that Mexican government officials or security agents demand bribes to let people join the list or move up the list. Several migrants waiting at the bridge said they had not been solicited for a bribe, and that the list was seemingly run fairly, but very slowly.

Migrants seeking asylum in the United States play at their encampment near the international bridge in Matamoros, Mexico, April 30, 2019. (AP Photo/Eric Gay)

The people who wait in the tents by the bridge have formed their own enclosed community. On a recent weekday morning, a woman from Honduras braided the hair of a woman from Venezuela. A child swung his hips with a hula hoop. Whistles and cheers went up when volunteers from a group called Team Brownsville arrived with a breakfast of milk, cereal, and boiled eggs.

But the encampment is a harsh place, especially in temperatures that already hit 90 degrees Fahrenheit (32 degrees Celsius) a month before summer starts. Some people scrape together 4 Mexican pesos — about 25 U.S. cents — to use the bathroom on the international bridge, and then come back.

One man climbed into the Rio Grande to bathe. The country he was waiting to enter was a short swim away, but he stayed close to the bank on the Mexican side.

And then he went back toward the tents. To wait.