A Republican senator is pressing the Biden administration over 85,000 unaccounted for migrant children released into the United States, according to a letter provided to Fox News Digital.

Tennessee Sen. Marsha Blackburn sent a letter to Health and Human Services Secretary Xavier Becerra on Thursday demanding answers for the "abuse and exploitation" of migrant children following reports of forced labor and whistleblower testimony alleging that the government is delivering some to human traffickers. 

"I am deeply concerned regarding the recent reports that the Department of Health and Human Services (HHS) has mishandled unaccompanied migrant children by placing them with unvetted sponsors, leading to their exploitation and forced labor," Blackburn wrote in the letter to Becerra. 

"President Biden's border crisis has placed illegal immigrants in dangerous—and often deadly— situations, and the over 250,000 unaccompanied minors who have crossed our southern border over the last two years are no exception," Blackburn wrote.

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

HHS Secretary Xavier Becerra

Health and Human Services Secretary Xavier Becerra said he was unfamiliar with the statistics regarding the agency's inability to contact migrant children.

Becerra appeared before the Senate Finance Committee in late March and said he was unfamiliar with the statistics regarding the agency's inability to contact the tens of thousands of unaccompanied child migrants released to sponsors after being encountered at the southern border.

"I have never heard that number of 85,000, I don't know where it comes from and …so I would say it 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," Becerra said.

"Congress has given us certain authorities," Becerra added. "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."

When unaccompanied children come to the border, they are turned over by Border Patrol to HHS, who attempt to find them a sponsor within the country -- typically a family member.

"When questioned at the hearing, you indicated that you were not aware that children were being forced to work in dangerous jobs for long hours, nor were you familiar with the fact that 85,000 children had gone missing under your watch," Blackburn wrote to Becerra. "While you claimed you were uninformed about this situation, reporting following your testimony indicates a grave dereliction of duty."

Blackburn demanded Becerra provide her office with answers to a series of questions, including when he learned of the mishandling and exploitation of migrant children released by HHS to unvetted sponsors and whether he was aware it is a crime under federal law to "knowingly and willfully" make a "materially false" statement to Congress, among other queries. 

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Senator Marsha Blackburn

Tennessee Republican Senator Marsha Blackburn is demanding answers from Becerra following reports of migrant child labor. (Kevin Dietsch/Getty Images)

Blackburn also requested any reports, correspondence, or other documentation he had received regarding the potential exploitation of the migrant children.

Blackburn's letter followed a New York Times report detailing a rise in child exploitation, where children are forced into the labor force — sometimes to pay back their smuggling costs.

The Times reported that while HHS checks on all minors by calling them a month after being released to sponsors, data showed that over the last two years, the agency could not reach more than 85,000 of them and lost immediate contact with a third of migrant children.

Some of those children had been trafficked and forced into dangerous jobs, the Times reported. 

A whistleblower further told Congress this week that the government is delivering migrant children to a "sophisticated network" of human traffickers.

Tara Lee Rodas, who was detailed with HHS at an Emergency Intake Site in Pomona, California, told lawmakers on Wednesday about what she experienced on the ground. 

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Tara Lee Rodas

Tara Lee Rodas, an HHS whistleblower, said the government is delivering some migrant children to a sophisticated network of human traffickers. (Screenshot)

"I thought I was going to help place children in loving homes," Rodas said. "Instead, I discovered that children are being trafficked through a sophisticated network that begins with recruiting in their home country, smuggled to the U.S. border, and ends when [Office of Refugee Resettlement] delivers a child to a sponsor — some sponsors are criminals and traffickers and members of Transnational Criminal Organizations."

"Some sponsors view children as commodities and assets to be used for earning income — this is why we are witnessing an explosion of labor trafficking," Rodas said.

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Republicans have blamed the ongoing border crisis on the Biden administration's policies, which they say have encouraged illegal migration and for parents to put their children into the hands of smugglers. 

Democrats have noted that the issue predated the Biden administration and have pointed to undertaken efforts to increase oversight of sponsors, along with new task forces, greater information sharing and calls for more significant funding.

HHS did not respond to a Fox News Digital request for comment.