LOS ANGELES (AP) — As tens of thousands of children fleeing violence in Central America crossed the border in search of safe harbor, overwhelmed U.S. officials weakened child protection policies, placing some young migrants in homes where they were sexually assaulted, starved or forced to work for little or no pay, an Associated Press investigation has found.

Without enough beds to house the record numbers of young arrivals, the U.S. Department of Health and Human Services lowered its safety standards during border surges in the last three years to swiftly move children out of government shelters and into sponsors' homes. The procedures were increasingly relaxed as the number of young migrants rose in response to spiraling gang and drug violence in Honduras, Guatemala and El Salvador, according to emails, agency memos and operations manuals obtained by AP, some under the Freedom of Information Act.

First, the government stopped fingerprinting most adults seeking to claim the children. In April 2014, the agency stopped requiring original copies of birth certificates to prove most sponsors' identities. The next month, it decided not to complete forms that request sponsors' personal and identifying information before sending many of the children to sponsors' homes. Then, it eliminated FBI criminal history checks for many sponsors.

"This is clearly the tip of the iceberg," said Jacqueline Bhabha, research director at the FXB Center for Health and Human Rights at Harvard University. "We would never release domestic children to private settings with as little scrutiny."

Advocates say it is hard to gauge the total number of children exposed to dangerous conditions among the more than 89,000 placed with sponsors since October 2013 because many of the migrants designated for follow-up were nowhere to be found when social workers tried to reach them.

Federal officials won't disclose details of how the agency was stretched so thin, but say they are strengthening the procedures as the number of young migrants once again is on the rise, and recently signed a contract to open new shelters.

"We are not taking shortcuts," HHS spokesman Mark Weber said. "The program does an amazing job overall."

YOUNG VICTIMS

One of the cases reviewed by the AP involved a then-14-year-old from Guatemala who arrived in the U.S. in September 2014 and was sent to a sponsor's tiny apartment in Los Angeles, where he was held for three weeks. In an interview, Marvin Velasco said his sponsor, a distant relative who he had never met, deprived him of food, which left him weak and praying for his salvation.

"He told authorities that he was going to take me to school and help me with food and clothing, but it wasn't like that at all," said Velasco, who since has been granted special legal status for young immigrants. "The whole time, I was just praying and thinking about my family."

Velasco's perilous journey from Guatemala included crossing a river, even though he doesn't swim, and getting lost at night in a frigid desert. Once in the U.S., he was apprehended by U.S. Border Patrol agents, processed in Hidalgo, Texas, and sent to a shelter run by HHS' Office of Refugee Resettlement.

Unlike the extensive screenings required in the U.S. foster care system, the ORR had stopped requiring that social workers complete extensive background checks or fingerprint most sponsors when they placed Velasco with his brother-in-law's father. Social workers did not visit the sponsor's one-bedroom apartment before he arrived or check up on him afterward, said Gina Manciati, the boy's attorney.

Velasco said he soon realized that nine other people lived there. The sponsor told Velasco he would be punished if he left the apartment, and demanded rent payments. When Velasco told the sponsor he wanted to study, the man called the boy's parents in Guatemala, threatening to kick him out if they didn't pay. Then the sponsor started withholding food, Velasco said.

With help from the sponsor's son, Velasco escaped and sought sanctuary in a nearby church, where he met a parishioner who took him in and became his legal guardian. Now 15 and living with a Guatemalan immigrant family that is raising him as their son, he is thriving in school and leads the church's devotional band.

Other accounts uncovered by the AP include:

— A 14-year-old Honduran girl whose stepfather forced her to work over a period of several months at cantinas in central Florida where women drink, dance and sometimes have sex with patrons.

— A 17-year-old from Honduras sent to live with an aunt in Texas, who forced her to work in a restaurant at night and clean houses on weekends, and often locked her in the home.

— A 17-year-old Guatemalan placed with a friend's brother in Alabama who vowed to help him attend school, but instead was made to work in a restaurant for 12 hours a day to earn rent.

— A Central American teen placed with a family friend who forced her to cook, clean and care for a group of younger children in a Florida trailer park.

— A Honduran teen placed with a sponsor in New York City who was so physically abusive that she ran away and sought refuge in a shelter.

Experts who work with migrant children, including a psychologist and an attorney, cited cases in which unaccompanied children were raped by relatives or other people associated with their sponsors.

Weber said the ORR has added more home visits and background checks since July, when federal prosecutors charged sponsors and associates with running a trafficking ring in rural Ohio that forced six unaccompanied minors to work on egg farms. Lured north with the promise of an education, the teens instead were forced to work under threats of death for up to 12 hours a day.

"These tragic situations do happen when there are bad actors involved, and that makes it incredibly difficult for the government to ferret them out," Weber said. "I know we learn from lessons and keep trying to improve the system to ensure the child is placed in a safe place, and I'm confident the vast majority of the kids are."

HOW THE PROBLEM EVOLVED

Contractors and advocates say that, starting in 2012, they repeatedly warned HHS about the steady increase in children arriving at the border. The agency itself warned case management staff in 2013 that "fraudulent sponsors" in Colorado, Iowa and Minnesota had sought to claim multiple, unrelated minors. By the summer of 2014, the challenge of dealing with a sea of unaccompanied minors had become a full-blown crisis.

"So many kids were piling up at the Border Patrol stations that the agency had to start emptying their shelter beds," said Jennifer Podkul, senior program officer at the nonprofit Women's Refugee Commission. "They sped up reunification procedures that they had in place for years."

By law, child migrants traveling alone must be sent to an ORR facility within three days of being detained. The agency then is responsible for the children's care until they are united with a relative or sponsor in the community they can live with while awaiting immigration court hearings. Sponsors can be parents, grandparents, distant relatives or unrelated adults, such as family friends, and all are expected to enroll the children in school, help them get health care and attend court.

In 2012, caseworkers followed a stringent process before releasing children to sponsors, including background checks, fingerprints, 60-day home studies and signed agreements that the children would appear in immigration court. But in November 2013, overburdened by a sudden influx of unaccompanied children, the agency took the first of what would be a series of steps to lower its standards, stating in a manual that most parents and legal guardians would not be fingerprinted.

ORR said the relaxed rules on the front end were compensated on the back end by more children getting social services attention after being released into the community. Even now, though, most young migrants rarely see child welfare workers after landing at sponsors' homes.

Only a small group of at-risk children who the government believes need extra protection are visited by social workers contracted by ORR, and the services cease when the children turn 18. But sometimes, those vulnerable children vanish before social workers reach them. Federal contractor Lutheran Immigration and Refugee Service has tracked 201 cases in which children ran away or the families couldn't be traced, which represents 11 percent of their closed cases since 2013.

Last year, a social worker visited an apartment complex in Fort Meyers, Florida, to see if it was suitable for a new placement. The government had sent more than a dozen other children to live there, but the social worker found nothing but an empty apartment, said Hilary Chester, associate director of anti-trafficking programs at U.S. Council of Catholic Bishops, another federal contractor.

"We were concerned that it could have been a front to have those kids released so that traffickers could get them into the workforce," Chester said. "No one knows where the kids are."

ORR bars releasing children to people who have been convicted of child abuse or neglect or violent felonies like homicide and rape. But in November, a whistleblower told Sen. Chuck Grassley, R-Iowa, that federal authorities had placed unaccompanied children with convicted criminals. The whistleblower alleged that 3,400 sponsors listed in a government database had criminal histories including homicide, child molestation, sexual assault and human trafficking, according to Grassley's office.

Weber, the HHS spokesman, said the agency's inspector general is reviewing the claim.

A NEW WAVE ARRIVES

As crime and violence deepen in Guatemala, Honduras and El Salvador — fueled in part by the cocaine trade and political instability — contractors worry that the latest wave of child migrants could approach the 2014 levels that spurred President Barack Obama to declare an "urgent humanitarian situation."

Federal immigration agents' recent controversial efforts to round up Central American families for possible deportation have further complicated the situation, creating a climate of fear and instability in communities that are welcoming children, and putting some minors who lack attorneys at risk of deportation, advocates said.

Weber said HHS is better prepared to accommodate the new child migrants, including preparing to add 2,200 shelter beds where children can stay while awaiting placement. A national call center where children and sponsors can report problems has been established, but Weber said children also should contact local authorities if they feel unsafe.

Last month, HHS Secretary Sylvia Burwell warned Congress the agency needed an additional $400 million to be able to provide shelter and referral services to the young migrants, but the request was denied.

After that, the agency directed contractors to speed up home visits to get children out of detention and into families' homes more quickly.

Sen. Rob Portman, R-Ohio, who chairs the Senate's bipartisan Permanent Subcommittee on Investigations, said he will hold a hearing on the agency's child placement program Thursday because he is concerned that the failures revealed in the egg farm case are systemic.

"We think reforms are necessary and urgently required because there are kids right now who are coming in over the border," Portman said. "This is a problem that has to be addressed."

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The AP National Investigative Team can be reached at investigate@ap.org