The Department of Homeland Security’s inspector general has recently reported on facilities that it found to be dangerously overcrowded, where there was standing room only, and where lights had been kept on 24 hours a day in rooms where people had been left to sleep on concrete floors. But reporters have rarely been allowed into the facilities to document the conditions first hand.

Mr. Trump refused to take responsibility for the conditions facing migrant children and families at border facilities. “You know, they were built by President Obama, they are really not designed so much for children,” Mr. Trump said in an interview in the Oval Office on Tuesday. “But you know, children can be there because we have no choice because of the laws, the laws are so bad.”

Asked if his administration’s policies were to blame, Mr. Trump said the conditions existed because Democrats in Congress would not agree to policy changes that would stanch the flow of migrants across the border. “All I can say is that if they change the law, you wouldn’t have it,” Mr. Trump said. “The cartels are making the money, are they using children’s — it’s virtual slavery. And if we could get a change, a very simple change it would go so quickly, so easily with the Democrats, we would be able to solve that problem very easily.”

[Meet the lawyer who didn’t want to promise a toothbrush to migrant children.]

The station in Clint was built in 2012. It was meant to temporarily house adults, not children, and not for a month at a time, as has happened under the Trump administration.

Local Democratic lawmakers on Tuesday were demanding an immediate improvement to conditions for detainees along the border, with Representative Joaquin Castro, a Democrat from Texas who is chairman of the Congressional Hispanic Caucus, announcing that the caucus would lead an inspection of the facility at Clint next week.