52 people have died as a result of a riot and a fire near Monterrey in northern Mexico.
Smoke was seen from the complex but officials said the situation is now under control.
A spokesperson confirmed that no inmates have escaped.
Relatives of inmates reported to local media that they had seen multiple inmates with burns, and that authorities were searching for escapees.
One relative threw rocks at guards. “I want to know that my daughter is OK. She is in the infirmary. There are children in there,” the woman said.
Pope Francis will begin his first trip to Mexico on Friday and will visit a prison in the city of Ciudad Juarez.
A spokesperson said the violence involved a brutal fight between rival factions, including one led by a member of the Zetas drug cartel.
All 52 victims were male and have not yet been formally identified.
