Thousands of migrant children who crossed the southern border into the U.S. have reported they were sexually assaulted while in government custody, according to Department of Health and Human Services documents released Tuesday by Rep. Ted Deutch’s office.

In the past four years, 4,556 children said they were sexually assaulted while in the care of Health and Human Services’ Office of Refugee Resettlement, which takes custody of unaccompanied minors who cross the southern border alone and those who are separated from their families.

Allegations go back to 2015, meaning the reported assaults started under the Obama administration. But the allegations have increased in the past two years after the Trump administration’s “zero tolerance” policy that led to at least 2,800 family separations flooding the department with additional children.

The data show the majority of the alleged assaults were carried out by other minors in custody, but at least 178 were carried out by staff.

“These documents detail an environment of systemic sexual assaults by staff on unaccompanied children,” said Deutch, a Democrat from Florida, in a House Judiciary Committee meeting Tuesday. […]