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The chairman of the House Homeland Security Committee accused the Trump administration of misleading Congress and the public about the death of a 16-year-old boy in Border Patrol custody, and he urged a swift completion of an internal investigation.

Rep. Bennie Thompson, D-Miss., said a report by ProPublica on the May 20 death of Carlos Gregorio Hernandez Vasquez “calls into serious question the steps U.S. Customs and Border Protection claims to have taken to care for a child in its custody.”

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“Not only did CBP hold Carlos longer than the legal limit and apparently fail to care for him while he was sick, the agency seems to have been untruthful with Congress and the public about the circumstances around his tragic death. This is inexcusable,” Thompson said in a statement Thursday evening.

A video obtained by ProPublica from the police in Weslaco, Texas, showed Carlos collapsing in his cell and lying on the floor for more than four hours, until another sick boy discovered his body and alerted a Border Patrol agent. A press release the day of his death from CBP, the Border Patrol’s parent agency, asserted, “He was found un-responsive this morning during a welfare check.”

ProPublica’s investigation also found numerous missteps by Border Patrol agents and health care workers during Carlos’ detention at facilities in McAllen and Weslaco in South Texas. CBP did not follow a nurse’s instructions to closely monitor him. It did not send him to a hospital as his condition declined. Agents did not notice or respond to his distress as he lay motionless on the concrete floor for more than four hours. He was in custody for six days, three more than is allowed for minors.

CBP officials declined to respond to a request for comment on Thompson’s statement. Officials have said they are limited in what they can say about Carlos’ death because of an ongoing internal investigation.

The agency also declined to respond to questions about Carlos’ death. “While we cannot discuss specific information or details of this investigation, we can tell you that the Department of Homeland Security and this agency are looking into all aspects of this case to ensure all procedures were followed,” CBP spokesperson Matt Leas said.

The Department of Homeland Security inspector general launched an investigation hours after Carlos’ death, and CBP has declined to provide the video to congressional committees.

Thompson called on the inspector general to “examine all video from Carlos’ time in custody, complete their investigation expeditiously, and release their findings as soon as possible.”

The inspector general, an independent arm of DHS, hasn’t responded to requests for information on the investigation into Carlos’ death.

Read More Inside the Cell Where a Sick 16-Year-Old Boy Died in Border Patrol Care Video obtained by ProPublica shows the Border Patrol held a sick teen in a concrete cell without proper medical attention and did not discover his body until his cellmate alerted guards.

Other Democratic officials criticized the Trump administration’s handling of children at the border in the wake of the ProPublica report.

In a tweet, the Congressional Hispanic Caucus said: “We now know that CBP lied about Carlos Vasquez’s death — CBP failed to provide critically necessary medical care & failed to notice his death until his cellmate discovered his body. This is criminal negligence — @HispanicCaucus will demand answers & accountability from CBP.”

Democratic presidential candidate Julian Castro tweeted: “We know now what we suspected then: @CBP did not provide adequate care, nor did they tell truth. This is what happens when we criminalize desperation and refuse to treat immigrants as human beings.”

The American Civil Liberties Union, which has filed numerous lawsuits challenging the Trump administration’s border policies, said the video “epitomizes the cruelty of CBP’s disregard for the lives of those in its custody.”