Two senators — a Democrat and a Republican — are demanding the U.S. government turn over information related to "horrific and intolerable allegations of excessive compensation, self-dealing, and sexual abuse" at federally funded facilities for unaccompanied migrant children.

In a letter to Health and Human Services Assistant Secretary for Children and Families Lynn Johnson, the senators — Finance Committee Chairman Chuck Grassley, R-Iowa, and ranking member Ron Wyden, D-Ore. — laid out requests for wide-ranging information about the nation's unaccompanied children shelter system.

"Recent reports detail horrific and intolerable allegations of excessive compensation, self-dealing, and sexual abuse perpetrated by these taxpayer-funded grantees," the senators wrote. "These allegations raise serious questions about how some grantees have used federal funding, and whether ORR has failed to uphold its statutory duties to ensure the health and safety of children within their care."

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The letter cites recent news reports alleging that Southwest Key, the nation's largest chain of shelters, engaged in self-dealing while enriching its founder, that the government is housing some children in secretive "out-of-network" shelters, and that there have been thousands of cases of sexual abuse in the past four years. The Department of Health and Human Services (HHS) has ardently disputed the figures on sexual abuse.

A spokesperson for HHS said Monday the department has "received the letter and will respond in a timely fashion."

The letter lists 29 questions and data requests that combined could provide a much more detailed look at the nation's system for sheltering tens of thousands of unaccompanied children annually. They are typically placed in shelters after they are apprehended near the southern border.

There are currently at least 168 shelters in 17 states. The largest such facility, in Homestead, Florida, can currently fit as many as 3,200 people.

The senators honed in on that facility, a "Tent City" that operated for roughly six months last year in Tornillo, Texas, and Southwest Key operations in their letter. In particular, they demanded copies of those sites' incident reports, which "range in severity from a verbal argument between two children to a sexual assault," according to federal policy.

The requests also include detailed information about every shelter operated since 2014, sexual abuse enforcement and prevention efforts, reunification practices and oversight policies.