Brayan Duvan Soler Redondo, a 14-year-old Honduran boy, overlooking the Rio Grande. He is staying at a migrant shelter in Reynosa. He is traveling alone and trying to get to the United States to find work to help his family. (Joshua Partlow/The Washington Post)

Susanna Torres was a dimple-cheeked preteen living lonely with her stepmother in El Salvador — her father had disappeared, her mother was on Long Island, N.Y. — when she hatched her plan.

For three years, she secretly socked away the money her mom sent for school until she had $6,000. It was enough to hire a smuggler and join the underground network of buses and train tops, through jungles and deserts.

She had one thing in mind when she left in her freshman year of high school to travel 1,400 miles north to the United States by herself.

“I wanted to be with my mom,” she said.

Instead, she found herself on the banks of the Rio Grande in early June, too exhausted to walk on. She ended up behind coils of razor wire in a home for child migrants run by the Mexican government, watching “Ice Age” on DVD as she waited to be deported.

Sudden surge in unaccompanied children at border

As migrants stream north from Central America, thousands of children such as Susanna are ending up alone and adrift in a border-land limbo. On the U.S. side, they are being crammed into Border Patrol stations designed to detain and deport single males, not provide food and care for third-graders without their parents. On the Mexican side, they are bunking down in the rough world of church shelters, surrounded by sunburned men heading north for work or reeling from deportation.

“Right now I’m small, but I’ve heard they’re giving minors the opportunity to work in the U.S.,” said Brayan Duvan Soler Redondo, a 14-year-old Honduran boy who has spent the past two weeks alone in a shelter here in Reynosa. “I have to trust in God to get me to the other side.”

The surge of juveniles across the Rio Grande in south Texas is a new challenge for U.S. immigration policy and the debate in Washington about whether to change it. Although the overall number of illegal migrants arrested along the southern U.S. border is still far lower than the 900,000 per year or more apprehended before 2006, U.S. agents are ill-equipped to deal with so many Central Americans, let alone children.

In the past, border cities on the Mexico side have been more likely to have large groups of deportees on their streets — not child travelers on their way north — as illegal immigration from Mexico plummeted to its lowest levels in 40 years. Shelters became filled with anxious fathers kicked out of the United States, desperate to swim the river or hike the desert at night to get back to jobs, wives and U.S.-born children.

The children and mothers coming now from Guatemala, El Salvador and Honduras are different. In many cases, they appear to be heading north to reunite with parents or husbands already in the United States. Some are being summoned by relatives because of rumors that the United States is offering “permits” for women and children to stay. The children, as young as 4, often arrive with no legal guardian but carry handwritten notes for the Border Patrol with relatives’ phone numbers.

To avoid the sweltering Texas heat, the border-crossers are fording the Rio Grande in large groups in the early evening, wading through shallow crossings or floating over in cheap dinghies. They follow dirt paths through cottonwood groves up to the levee roads where Border Patrol vehicles are parked every night, waiting. “Sometimes they’ll come right up and knock on your windows,” said Chris Cabrera, an agent and Border Patrol union spokesman.

On one recent evening, a group of 15, including a woman with a baby strapped to her back and seven other children, emerged from the brush and climbed up the levee. They waited on the gravel road for the Border Patrol trucks to arrive, making no attempt to flee or hide.

“Are there any unaccompanied minors?” one border patrol agent asked in Spanish, as he took down names and nationalities. “Who came alone?”

A thin boy in an Aeropostale T-shirt raised his hand.

More children are on their way. A draft of an internal Border Patrol memo for the White House from last month estimated that the number of unaccompanied minors detained by the border patrol will reach 90,000 this year, higher than expected, and rise to 142,000 next year. President Obama has declared a humanitarian crisis and pledged $2 billion to build temporary housing for the new migrants. Thousands of unaccompanied children picked up by Border Patrol are being held on military bases and in converted warehouses if they don’t have parents or guardians who can claim them.

Texas Attorney General Greg Abbott (R) requested $30 million from the Department of Homeland Security on Thursday to send more law enforcement officers to the border, because children have “so overwhelmed the U.S. Border Patrol that federal agents are devoting time and resources to the humanitarian aspects of the influx, and are not available to secure the border and successfully stop criminal activity,” his office said in a statement.

For those detained by Mexican authorities before they reach the United States, many will be deported. Some of these children await removal at the Attention Center for Border Minors, a government-run shelter in Reynosa, where as many as 400 children arrive each month.

“The majority of their parents are already in the United States. That’s the main reason the children are coming,” said José Guadalupe Villegas García, the organization’s director, who said he thinks U.S. immigration rules have gone lax. “This was something President Obama ordered.”

Maynor Delgado, a 16-year-old from Guatemala, has spent 84 days at the shelter, watching TV and making bracelets to pass the time, calling his family on Fridays, unsure whether he will be deported or released. “I don’t know how my papers are,” he said.

His parents gave him $7,000 to pay a guide and join five others — none of them relatives — on the journey from his home town of Quetzaltenango, an 11-day trek by taxi, train and bus, with stays at crowded stash houses and campsites, eating occasionally and sleeping on the ground. He has an older brother in Washington and wanted to join him to help support his parents.

“My family is poor. My mom washes clothes,” he said. “I’ll do whatever I can find.”

On his journey north, Brayan, the Honduran boy, parted ways with his elder brother after a fight over money. Left on his own, Brayan said he begged for food and rides along the way, until he arrived at a church in Reynosa, and eventually to Path of Life, a private migrant shelter. “I’m traveling with empty pockets,” he said, patting his shorts. “Zero.”

He has no money to pay for a guide across the river and is afraid to venture out into city streets controlled by the kidnapping and drug-trafficking cartel.

“I have no idea how long I’m going to be here,” he said.

Susanna Torres’s mother, Rosa, a 39-year-old nursing-home employee in Huntington, Long Island, didn’t know until she received a phone call this month from the Mexican shelter that her daughter was traveling to find her. “I had no idea,” she said. “I was very worried.”

She has talked with a lawyer about her daughter’s chances of being with her and her two other children in the United States but was told it’s a “slow process.”

“I want to be with my daughter, but there’s nothing I can do,” she said. “To be with your kids is the most important thing in life. I only ask God that he protects her.”

David Nakamura in Washington contributed to this report.