Department of Homeland Security (DHS) Secretary Kirstjen Nielsen struggled to answer questions from House Democrats about her role in implementing the Trump administration’s strict immigration policy and the subsequent family separation during her first hearing.

At one point during Wednesday’s testimony, Ms Nielsen denied that migrant children separated from their families at the border were held in cages.

“Sir, they are not cages, they are areas of the border facility that are carved out for the safety and protection of those who remain there while they’re being processed,” she responded during a tense exchange with House Homeland Security Committee Chair Bennie Thompson.

The DHS Secretary’s understanding of the situation was later questioned by Representative Bonnie Watson Coleman, who asked Ms Nielsen to elaborate on the facilities where children were held - and whether they differed from where dogs are kept.

Ms Nielsen appeared unable to differentiate between the Customs and Border Protection facilities and dog cages, telling Ms Watson Coleman: “It’s larger, it has facilities, it provides room to sit, to stand, to lay down.”

The response prompted Ms Watson Coleman to reply: “So did my dog’s cage.”

Despite the practice of separating families at the border ending with an executive order by the president, Ms Nielsen told the committee the crisis at the border is not “manufactured”.

“This is truly an emergency,” she said.

Following the hearing, Senator Jeff Merkley disagreed with Ms Nielsen’s insistence that children were not held in “cages”.

“I saw them with my own eyes. They’re cages. With children in them,” he wrote on Twitter.