The death was listed in the report as a suicide by self-strangulation and hanging. Law enforcement officials reviewed video recordings of what happened in the cell overnight, the report said.
“C.B.P. takes every loss of life very seriously and has initiated an internal review to ensure these policies were followed,” the agency’s statement said, referring to the agency’s standards on transport, escort, detention and search.
Representatives from the Starr County Sheriff’s Office did not return multiple calls and emails for comment on Saturday. A person who picked up the phone there said staff members were not available on weekends.
On May 7, days before Mr. Muñoz was apprehended at the border, Attorney General Jeff Sessions announced that the Trump administration would criminally prosecute everyone who illegally crosses the Southwest border, in what he called a “zero tolerance” policy intended to deter new migrants, mainly from Central American countries like Honduras.
The policy imposes potential criminal penalties on border-crossers who would have previously faced mainly civil deportation proceedings — and in the process, forces the separation of families crossing the border.
Many who have criticized the policy have focused on its effect on children who are separated from their parents.
But Justin Tullius, a lawyer at the nonprofit Raices, which works with migrants in Texas, said adults who are detained have also suffered.
“We’ve worked with parents who have shared suicidal thoughts and who have attempted to take their own lives because of the experience of detention,” Mr. Tullius said. “We can’t allow policies that traumatize parents and children. Families must be allowed to go through the process of seeking protection in the U.S. together, without unnecessary and harmful separation.”