At least thirty-one inmates were killed and other 13 were wounded in a brutal fight inside a prison in the northern Mexican state of Tamaulipas, the state's public safety department said in a statement on Wednesday.
Clashes between prisoners wielding makeshift knives, clubs and stones took place in the Santa Amalia prison in the city of Altamira, an overcrowded facility designed to hold 2000 inmates but which has a population of more than 3000.
The fight broke out when a group of inmates burst into a section of the prison they were banned from and attacked the prisoners housed there.
Federal police forces and soldiers surrounded the prison. Later, soldiers and marines moved in and regained control of the situation, the statement read.
The public safety department said 22 of the inmates killed had been serving sentences for state crimes and nine for federal offences.
Deadly riots and prison fights are common in Mexico's overcrowded prisons.
Powerful drug cartels are fighting for control of smuggling routes along the US-Mexico border. Gang rivalries frequently spread into Mexico's prison system, where prisoners held on federal drug charges are mixed with common criminals.
