Officials say members of the hyper-violent Zetas drug cartel stabbed and bludgeoned 44 members of the rival Gulf cartel to death and then staged a mass escape, apparently with the help of prison authorities.

The governor of the northern state of Nuevo Leon says the prison's director and three other officials have been fired and are under investigation for purportedly helping in the escape.

Gov. Rodrigo Medina said Monday that 30 inmates escaped during the Sunday riot, all of them Zetas. Medina said all the dead were from the Gulf gang.

The two gangs were former allies, but split in 2010 and have been fighting turf battles in Monterrey and elsewhere.

Medina offered a reward for the escaped inmates.