A 15-year-old boy has been reported missing in Texas after he ran away from a migrant children’s center and disappeared into the borderland. The Casa Padre center in Brownsville is the largest migrant child-care center in the U.S. and has come under intense scrutiny since it began housing children separated from their parents under President Trump’s “zero-tolerance” immigration policy. A spokesman for Southwest Key, the company that operates Casa Padre, said it couldn’t force children to stay on the premises if they wanted to leave and that “from time to time” children had walked out of its shelters. “We are not a detention center,” spokesperson Jeff Eller said in a statement, adding: “We talk to them and try to get them to stay. If they leave the property, we call law enforcement.” Federal officials did not respond to a question from The New York Times about how many children had walked away from migrant centers across the country. The 15-year-old boy was an unaccompanied and undocumented minor and had been under the care of the Southwest Key facility for 36 days, according to CNN.