Unaccompanied children continue to be one of the government’s biggest and most complex immigration challenges, Trump administration officials said Thursday.

In testimony before a Senate Homeland Security subcommittee, senior officials with the Departments of Homeland Security (DHS) and Health and Human Services (HHS) told lawmakers that federal agencies are struggling to process and keep track of migrant children after they are caught illegally crossing the southwest border.

Illustrating the point, Steven Wagner, the acting head of HHS’s Administration for Children and Families, revealed that his agency lost track of nearly 20 percent of the migrant children placed with sponsors during a three month period last year.

From October to December 2017, officials at the HHS’s refugee office contacted 7,635 children and their sponsors, but were unable to determine with certainty the whereabouts of 1,475 of them, Wagner said in prepared testimony.

Details of the unaccompanied alien children (UAC) programs came as Congress seeks to evaluate how federal agencies ensure migrant children in their care are tracked as they wind their way through years-long immigration court proceedings. Government watchdogs have found deficiencies in the programs, despite a February 2016 memorandum of agreement between DHS and HHS to establish new guidelines for handling UAC cases.

In most cases, children who cross the border without family are detained by Border Patrol agents or turn themselves in at the ports of entry. Once they are processed by immigration authorities, they are turned over to the custody of HHS’s Office of Refugee Resettlement.

The number of UAC and family cases has spiked after falling to recent lows last spring. In all of fiscal year 2017, immigration authorities referred 40,810 children to ORR, which is responsible for finding sponsors for UACs. In the first six months of fiscal 2018, HHS has had 21,574 referrals, putting it on pace for a 6 percent increase.

After slowing to a trickle in the early months of the Trump administration, monthly UAC referrals are approaching levels last seen during the Central American migrant crisis of the Obama administration’s last three years. HHS received 755 UAC referrals in March 2017, compared to 4,205 in March of this year — a 450 percent year-over-year increase.

The increasing flow of UAC and family units is putting stress on a multi-agency system that already struggles house children in its care and, crucially, keep track of them once they are placed with sponsors. A Government Accountability Office report presented to lawmakers found that HHS’s refugee agency is not adequately monitoring contract shelters it runs and is deficient in conducting mandatory home studies for UAC placed with non-family sponsors.

Thursday’s hearing also revealed that HHS does not currently have a system in place to guarantee that UACs attend immigration court dates after they are released to sponsors. HHS is supposed to make sure sponsors send their migrant children to immigration proceedings, but the agency has no way to enforce this requirement, said Sen. Rob Portman, the chairman of the Homeland Security subcommittee on investigations.

Under current law, HHS is not legally responsible for children after they have been released into the care of sponsors. But agency officials are re-evaluating their interpretation of the law to make sure that UAC don’t become victims of human trafficking or miss their immigration court dates, Wagner said.

“Based on what we have learned so far, if ORR were to remain legally obligated for the welfare of UAC after their release to a sponsor, or took on additional protective measures even if not legally obligated, those procedures would require a significant expansion of the current program structure and an increase in resources, and possibly additional legal authorities to further clarify,” Wagner said in his prepared remarks.

Follow Will on Twitter

Send tips to will@dailycallernewsfoundation.org.

Content created by The Daily Caller News Foundation is available without charge to any eligible news publisher that can provide a large audience. For licensing opportunities of our original content, please contact licensing@dailycallernewsfoundation.org.