Democratic members of the Senate and House announced legislation Thursday that seeks to make unlicensed detention facilities for unaccompanied migrant children illegal. If it becomes law, it would effectively shutter the country's largest facility in Homestead, Florida.

The bill proposed by Senator Jeff Merkley, D-Oregon, and Rep. Judy Chu, D-California, would outlaw "temporary emergency shelters" operated by the U.S. Department of Health and Human Services (HHS). Under agency guidelines, the designation allows such facilities to forego state licensing and frequent surprise inspections by state regulators.

The agency currently operates about 100 shelters nationwide for unaccompanied migrant children, but just one — the Homestead facility — is designated a "temporary emergency shelter." Another such facility in Tornillo, Texas, was closed in January. In a letter sent to the Justice Department on December 31, immigration attorneys identified a dozen more facilities that they said were also potentially operating without licenses. Those facilities have not been labeled "temporary emergency shelters" by HHS, and it is not clear why they might not have licenses.

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Merkley and Chu's bill, nicknamed the "Shut Down Child Prison Camps Act," specifically calls attention to the former Tornillo site and the Homestead facility, which as of February 3 housed 1,350 children -- about 12 percent of the nation's 11,200 unaccompanied minors, according to HHS.

An expansion to fit 1,000 more children was announced in late December, the same day HHS confirmed it would be closing the controversial Tornillo "tent city."

CBS News reported in January that because the Homestead facility is not licensed, its operator, Comprehensive Health Services, is not able to access Florida's child abuse and neglect employee background check system. The database includes child welfare history information that would not be surfaced by a standard FBI fingerprint background check.

In a statement to CBS News, Merkley criticized the choice to allow a company that cannot access that system to operate the country's largest shelter.

"It is horrific and unacceptable that migrant children are being locked up in Trump's Homestead child prison camp, and even more alarming that the for-profit company that runs the camp doesn't conduct background checks for child abuse on their staff," Merkley said.

Requests for comment from HHS and Comprehensive Health Services's parent corporation were not immediately returned.