On the heels of alleged abuse and mismanagement at several Health and Human Services shelters housing migrant children separated from their parents, the agency's inspector general has launched a review of these facilities, the inspector general's office confirms.
They expect to release a report by the end of 2018.
Citing conditions at the Shenandoah Valley Juvenile Center in Virginia and Southwest Key facilities across Texas, the lawmakers said they're concerned HHS "is actively working in ways that harm children."
Azar's office did not immediately respond to ABC News' request for comment.
As of last Wednesday, HHS had around 12,000 migrant children – including more than 2,000 children separated from their parents at the border under Trump's "zero tolerance" policy, which has since been amended to keep children detained alongside parents – in their custody.
According to records obtained by ABC News, state inspectors in Texas identified nearly 250 violations at facilities run by Southwest Key, one of HHS's biggest shelter contractors.
"Deficiencies" at those facilities included reports of a child with "unsupervised access to a tool/knife," a child "clearly in pain" not given prompt medical care, a child administered a medication to which she was allergic, and an employee writing obscenities on a chalkboard.
The company says staffers investigated each deficiency and "strive to provide the highest quality of care possible."
The letter to Azar points to even more troubling allegations reported by the Associated Press, including children with mental health issues "routinely beaten while shackled," and subjected to "long periods of solitary confinement."
"We are concerned that these immigrant children, with their existing vulnerabilities, are falling prey to neglect and intentional harm," the lawmakers wrote.