Authorities believe the fire was caused by a protest initiated by some of the migrants detained at the center "after we think, they found out they’d be deported,” according to Mexican President Andrés Manuel López Obrador. Based on initial reports, migrants fearing deportation put small mattresses at the door of the shelter and set them on fire "as a form of protest," López Obrador said in a press conference Tuesday morning. "They didn’t imagine this would cause this misfortune." The fire began after 9 p.m. Monday night at the migration center run by the National Migration Institute in Ciudad Juárez, the agency said in a statement. The migrants at the facility had been detained by authorities.