A fight between prison inmates associated with rival drug gangs killed 44 inside a jail near the city of Monterrey in the state of Nuevo León, local authorities said on Sunday.

Jorge Domene, the state public security spokesman, told reporters that the victims were stabbed, stoned and beaten to death with bars.

The prison, in the municipality of Apodaca about 140 miles from the border with Texas, houses inmates associated with both the Gulf cartel and their bitter enemies in the Zetas cartel. The two groups have been involved in bitter turf wars in north-east Mexico for the past two years.

Domene said the prison fight broke out around 2am on Sunday morning after prisoners from C block attacked those in D block and that most if not all the victims were from the latter. He did not specify to which group they belonged.

"We hope that once the bodies are identified, we'll be able to say who was responsible for the attack," the official said.

Domene added that all the prison officers on duty at the time of the violence have been detained to aid an investigation into the possibility that some colluded in the attack. Prisoners from rival gangs are supposed to be kept apart.

Already escalating violence between Mexico's different drug cartels exploded after Felipe Calderon, the country's president, launched an all out offensive against organized crime in December 2006. At least 50,000 people have been killed since then, and the prisons are now filled with drug war related detainees.

With the gangs taking their rivalry behind bars – aided by pervasive corruption – deadly prison riots and massacres have become a regular feature of the drug wars. They are often accompanied by mass breakouts. Occasionally, the prison violence has involved firearms smuggled into the jails.

According to the national newspaper El Universal, there have been 267 deaths behind bars in 19 separate events since the government offensive began. Last month a riot in a prison in the north-east state of Tamaulipas left 31 dead. The paper said that the latest violence in Nuevo León was the worst prison bloodbath so far.

Relatives of the approximately 3,000 prisoners in the jail gathered outside the facility on Sunday morning demanding information. At one point some attempted to break down the a gate into the jail.