At least 39 people were killed after a fire broke out late Monday night in the sleeping area at a Mexican migrant facility near the U.S. border housing migrants from Central and South America. Most of the dead were Central Americans, although some were from Venezuela, said President Andrés Manuel López Obrador. Dozens others were injured and are in “delicate-serious” condition, according to the National Immigration Institute. They have been transferred to local hospitals. Firefighters and military personnel extinguished the flames.

A legal action to identify the migrants who died is ongoing contacting the consulates of different countries. Authorities are also investigating the cause of the fire. It appeared the fire was sparked during a protest by migrants who had been informed they were going to be deported. The national immigration agency said Tuesday that it “energetically rejects the actions that led to this tragedy.” This was one of the deadliest incidents ever at an immigration lockup in the country. Mexico’s attorney general’s office has launched an inquiry. Ciudad Juarez is a major crossing point for people entering the United States. Shelters are full of people waiting for opportunities to cross into the U.S.