The death toll from Tuesday's riot at the Cadereyta prison in northern Mexico rose to 16 on Wednesday, the prosecutor-general of the state of Nuevo Leon announced.
In a press conference, Bernardo Gonzalez said that an investigation was ongoing to determine the exact cause of the deaths.
He added that at least 54 people are being investigated for their part in the riot, which happened for over eight hours in the prison located 45 km outside the state capital of Monterrey.
The riot started when prisoners took three guards as hostages, led them to the top of a dormitory block and threatened to throw them off the roof, according to an official report.
The state police entered the prison and had to use lethal force to end the riot by prisoners, who had set fires in several areas to prevent the entry of security forces, according to Aldo Fasci, director of the information center for state security.
This is the second riot this year at Cadereyta after a riot in March left four dead and several others injured.