FIRST ON FOX: Dozens of Republican lawmakers in the House and Senate are slamming the Biden-Harris administration's handling of the hundreds of thousands of unaccompanied migrant children who have come into the U.S. since 2021 – alleging a "cover-up" of information and how policies have led to potential exploitation.

Sen. Chuck Grassley, R-Iowa, led lawmakers in a lengthy letter to President Biden and Vice President Kamala Harris, accusing the administration of failing unaccompanied migrant children "by rushing them out of the custody of your Department of Health and Human Services (HHS) Office of Refugee Resettlement (ORR) into the hands of unvetted sponsors who often continue to exploit and abuse them."

More than 500,000 unaccompanied alien children (UAC) have crossed the border without a parent or guardian since 2021. When unaccompanied children come to the border, they are currently turned over by Border Patrol to Health and Human Services (HHS) who will attempt to find them a sponsor within the country -- typically a family member.

THOUSANDS OF MIGRANT KIDS MISSING ACCORDING TO WATCHDOG REPORT, GOP SENATOR SLAMS DHS: ‘RECKLESS DISREGARD’ 

Migrants walk along the highway through Suchiate, Chiapas state in southern Mexico, Sunday, July 21, 2024, during their journey north toward the U.S. border. ((AP Photo/Edgar H. Clemente))

The letter claims the administration has cut back on background checks and vetting procedures, as part of an effort to speed up the process. They say the administration "continued Vice President Harris’s longtime priority of cutting back on information sharing between HHS ORR and law enforcement related to unaccompanied children and sponsors."

The letter is led by Grassley, and includes Senate Homeland Security Committee Ranking Member Ron Johnson, House Judiciary Committee Chairman Jim Jordan, Senate Health, Education Labor and Pensions Committee Ranking Member Bill Cassidy and House Immigration Subcommittee Chairman Tom McClintock. 

The lawmakers point to moves by the administration to limit familial DNA testing, and Trump-era proposals to provide post-release check ups for those handed over to sponsors.

The issue came into the spotlight last year when the New York Times reported on how the agency has been unable to reach 85,000 minors and lost immediate contact with a third of them.

HHS Secretary Xavier Becerra said at that time that the number "doesn’t sound at all to be realistic" and "what we do is we try and follow up as best we can with these kids."

"Congress has given us certain authorities. Our authorities end when we have found a suitable sponsor to place that child with. We try and do some follow up but neither the child or the sponsor is actually obligated to follow up with us," he said.

ICE LOST TRACK OF TENS OF THOUSANDS OF MIGRANT KIDS, DHS INSPECTOR GENERAL FINDS

Sen. Chuck Grassley, R-Iowa, led the letter to President Biden and Vice President Harris. (Al Drago/Bloomberg via Getty Images)

This year, the Department of Homeland Security’s Inspector General sent a report to Congress finding that, over the past five years, more than 32,000 UACs did not show for immigration court hearings, and that Immigration and Customs Enforcement could not account for the location of all of those who did not appear. 

The lawmakers said that HHS ORR is "actively attempting to cover up the results of its egregious decisions" to roll back vetting, also accusing the administration of silencing whistleblowers. The letter also says that DHS recently informed Grassley's office that HHS has not complied sufficiently with two out of three subpoenas/information requests from his referral of possible child trafficking rings.

"By not supplying the information law enforcement requested, ORR denied Homeland Security Investigations (HSI) agents critical information, including the last known addresses of children and sponsors and the identity of other household members," the letter says.

They also argue that HHS's alleged failure to vet sponsors has led to the ignoring of possible gang affiliations, with no policy in place to refer suspected gang members for prosecution or investigation. It highlights the death of Kayla Hamilton, allegedly at the hands of an unaccompanied migrant.

HHS CHIEF ‘UNFAMILIAR’ WITH REPORTS THAT AGENCY CAN'T CONTACT 85,000 UNACCOMPANIED MIGRANT KIDS  

"HHS must stop its cover-up and cooperate with law enforcement and Congress to end this crisis and protect unaccompanied children and the American people," they say. Fox reached out to the White House and HHS for comment.

CLICK HERE FOR MORE COVERAGE OF THE BORDER SECURITY CRISIS

The letter comes as immigration remains a top 2024 issue. Republicans have pointed to the historic crisis at the southern border and tied it to the "open borders" policies of the administration.

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The administration says that those numbers have dropped sharply in recent months after President Biden signed an executive order limiting asylum claims at the border. It has called on Republicans to support a bipartisan border security bill unveiled earlier this year. Republicans have said that bill will codify high levels of illegal immigration.