Local news outlet Milenio TV reported several prisoners may have escaped, according to Reuters. Of the 12 people injured, 5 are in critical condition. The 52 victims were all male, said Nuevo León governor Jaime Rodríguez Calderón.
Calderón said the riot involved a violent fight between rival factions within the prison. The fire began shortly after midnight and was accompanied by shouts and explosions, the Associated Press reported, citing witnesses.
Images broadcast on the television channel depicted rescue workers removing inmates from the facility. Pope Francis had planned to visit another nearby prison next week during a tour of Mexico.