A riot and a fire at a prison near Monterrey in northern Mexico has left 52 people dead, state officials say.
Another 12 were injured in the riot at Topo Chico jail that broke out just after midnight.
Smoke was seen billowing from the complex but officials in Nuevo Leon state say the situation is now under control and no inmates have escaped.
Crowds of people worried about relatives inside the jail blocked roads outside, demanding information.
“I want to know that my daughter is OK. She is in the infirmary. There are children in there,” one woman said.
The incident comes just days before Pope Francis is due to visit a prison in the northern city of Ciudad Juarez, an area notorious for violence between drugs cartels.
There was no official word on how many people had died in Topo Chico until a statement by Nuevo Leon state Governor Jaime Rodriguez several hours after trouble broke out.
“We are experiencing a tragedy,” he said.
“The authorities formed a security cordon and nobody escaped. Everything was under control at 1.30am,” state public security spokesman Antonio Arguello told AFP news agency.
Witnesses reported hearing shouts and explosions when the fire began in the early hours.
Mexican newspaper El Universal said one of four buildings in the prison had been set alight by inmates burning furniture and rubbish.
The cause of the riot was not clear. One report said it had been triggered by an escape attempt by prisoners belonging to the notorious Zetas drugs cartel.
Gang violence and break-outs are common in Mexico’s notoriously overcrowded and corrupt prison system.
In 2013, 13 people died in a battle between inmates at the La Pila jail in the central state of San Luis Potosi.
A year earlier, 44 inmates were killed in a riot at the Apodaca prison in Monterrey. Another 30 prisoners escaped. The prison’s director was later sacked.