A fire that killed 39 migrants who were about to be deported from Ciudad Juarez highlights the increasing tension over Mexico’s continued crackdown on migrants aiming to reach the U.S.

The incident on Monday night, one of the deadliest in recent history at the Mexico-U.S. border, was provoked by Venezuelan and Central American migrants in a facility in the city bordering Texas, said President Andres Manuel Lopez Obrador on Tuesday morning. The fire was started slightly before 10 p.m. in the male-only center for adults, the National Immigration Institute said in a statement.

“This had to do with a protest that they started when they realized that they were going to be deported, moved, and as a protest they put cots in the door of the shelter and they set them on fire,” said AMLO, as the president is known, at a press briefing. “It’s very sad that this has happened.”

Another 29 migrants were injured by the fire and were transferred to local hospitals, some in serious condition, the statement added. The severe injuries and burns are making the process of identifying victims more complicated, said Venezuela’s Ambassador in Mexico Francisco Arias Cardenas.

The dead have yet to be identified by name, the president said.

In 2022, Mexico’s immigration authorities returned over 100,000 people to their countries of origin. The majority were from Central America but in recent years, Mexico has seen a growing number of people traveling from other countries, ranging from Haiti to Ecuador, with some arriving from as far as India and Russia.