(CNN) -- Twenty inmates were killed and 12 injured during a fight Saturday at a prison in northeastern Mexico, officials said.
The fight at the prison in Matamoros, in the northern border state of Tamaulipas, started early in the morning, according to a statement from state's public security secretariat.
With the help of police, prison officials restored order, it read.
Efforts were being made to contact the inmates' families.
The fight followed another in the Mexican state of Nuevo Leon this week.
At least seven inmates were killed and 20 were injured during a riot there on Thursday. Four of the inmates burned to death after inmates set mattresses on fire, while three died of stab wounds, authorities said.
In May, 14 inmates died in a fire at a prison in the nearby municipality of Apodaca. Dozens more were injured.