The acting commissioner of Customs and Border Protection will step down next week in the wake of reports that hundreds of detained migrant children are being housed in squalid and unsafe conditions at one of the agency’s centers in Texas.

John Sanders’ resignation comes as the Trump administration is struggling to handle the surge of migrants arriving at the US border from Central America. In a letter to Border Patrol staff, Sanders said he would step down on July 5, but did not give a reason.

“I can unequivocally say that helping support the amazing men and women of CBP has been the most fulfilling and satisfying opportunity of my career,” he wrote.

The agency announced on Tuesday that it had to return more than 100 children to a station in Clint, Texas, due to a lack of beds at other shelters.

A group of lawyers who recently visited the Texas facility found hundreds of children as young as 7 sleeping on the floor, lacking food and clothing, having inadequate medical care and living in overcrowded conditions for months. Some of the oldest children were found caring for toddlers.

“I’m very concerned,” President Trump said when asked about conditions at the border during an event in the Oval Office. “And they’re much better than they were under President Obama, by far.”

Earlier, acting Immigration and Customs Enforcement chief Mark Morgan acknowledged that minor migrants are being housed in “unsafe” conditions but blamed congressional Democrats for holding up funding that would allow the administration to address the situation.

“The border patrol stations, they were designed [to hold] adults only for a few hours and be removed,” he told “Fox & Friends.” “They are overcrowded. They’ve got hundreds of children in there.”

House Democrats on Tuesday evening appeared confident they would pass a $4.5 billion border-aid package after a revolt by the liberal wing of the party about the legislation.

Progressive House Democrats, like Rep. Alexandria Ocasio-Cortez, had threatened to vote against the bill because it would funnel money to agencies that have implemented Trump’s immigration policies.

With Wires