WASHINGTON (Nexstar) — Emotions ran high in the House Oversight and Reform Committee Thursday as the acting chief of Homeland Security failed to answer questions from Democrats about migrant family separations and poor conditions in detention centers.

Kevin McAleenan said Congress is to blame for the problems and that his department is doing all it can to manage the problem of children detained at the US-Mexico border.

“We’re doing our level best,” McAleenan said.

“What does that mean?” committee chair Elijah Cummings shot back. “What does that mean when a child is sitting in their own feces?”

Rep. Jackie Speier, a California Democrat, visited the border last week. She held up a picture of caged children. “This is familiar to you, seeing families, mothers and children caged with Mylar blankets?”

Lawmakers scheduled this hearing to follow the release of a new report on child separation. When McAleenan couldn’t answer questions about the report, Speier expressed her frustration.

“Here’s the problem,” she said. “You’ve had this report since last Friday. You should have come prepared to answer these particular cases.”

McAleenan agreed facilities at the border aren’t appropriate for housing children but said Congress hasn’t done enough to address the problem since he first identified it a year ago.

“I and CBP leaders have warned of the border security and humanitarian challenges in more than 100 meetings and briefings on the Hill,” he told the committee.

He added perceptions of a loophole in US laws lead to child trafficking.

“We’ve had egregious cases including a 51-year-old man who bought a 6-month-old child for $80 in Guatemala and admitted that when confronted with a DNA test.”

Ultimately, he said, Congress is responsible for the problems that stem from broken immigration and asylum laws.