A prison riot in Monterrey, Mexico, has left 52 people dead and a dozen injured, officials said Thursday.
The riot broke out as the result of fighting between rival groups of inmates at the Topo Chico prison in Monterrey in north-eastern Mexico. It was not the result of a mutiny and attempted prison break as initial reports had incorrectly indicated.
"We are living a tragedy," Jaime Rodriguez, governor of Nueva Leon state, said.
The incident began just before midnight, but the situation had been brought under control by early Thursday, officials said. One of the groups was led by Juan Pedro Saldivar, alias Z-27, a prominent member of the Los Zetas drug cartel.
Television images showed smoke rising from the prison and officials said there had been a fire in the prison's cafeteria, but it had not affected the cell blocks.
The incident comes one day before Pope Francis is due to arrive in Mexico for a visit that includes a stop at another prison in Ciudad Juarez along the US-Mexican border.
Media said alarmed relatives of the prisoners gathered outside the jail and threw stones and blocks of wood in a bid to break in.
The authorities were working to provide reliable information as soon as possible to the relatives to assure them of their loved ones' well-being.
Five of those who were injured were in serious condition.