Nuevo Leon state public security spokesman Jorge Domene Zambrano said the riot broke out at about 2 a.m. in a high-security section of a state prison in the city of Apodaca outside the northern industrial city of Monterrey.
The fight between two cell blocks, each with about 750 prisoners, may have been staged as a cover for a prison break, he said. Domene said in counting the dead, officials discovered some prisoners missing, but didn't know yet how many.
Forty-four people died before state police regained control about two hours later.
Investigators are looking into whether the fight was started by members of the rival Gulf and Zeta cartels, once the same organization. Their split two years ago has caused a spike in violence in the region around Monterrey, Mexico's third-largest and once the country's symbol of development and prosperity.
The prison had members of both gangs, who were normally separated, fueling theories that the 17 guards on duty could have been involved. The prison director, the director of security and a supervisor also are being held, Domene said.
The victims died from makeshift knives and blows, Domene said, adding that no firearms were found among the prisoners.
Deadly fights happen periodically in Mexico's prisons as gangs and drug cartels stage jail breaks and battle for control of penitentiaries, often with the involvement of officials. Sunday's riot was one of the deadliest so far.
All 2,500 inmates in the prison were incarcerated for federal crimes, and as many as 70 percent had yet to be convicted, Domene said. The inmate population grew by 1,500 in the last year to 180 percent capacity, the result of a crackdown on organized crime and drug trafficking in the last year, he added.
More than 47,500 people have been killed in drug-related violence since 2006, when President Felipe Calderon intensified Mexico's crackdown on organized crime.
Families of prisoners protested outside the prison because they couldn't get information on the victims. Only 10 of the dead had been identified by late afternoon.
The Apodaca prison was also the scene of a fire last May that killed 14. Officials then said the blaze could have been caused by a short circuit, not a prisoner uprising.
The bloodshed Sunday was just the latest in a string of deadly prison riots in Mexico in recent years.
Thirty-one prisoners died in January during a prison riot in the Gulf coast city of Altamira in Tamaulipas state, which borders Texas. Another fight in a Tamaulipas prison in the border city of Matamoros in October killed 20 inmates and injured 12.
Last July, a riot at a prison in the border city of Juarez killed 17 inmates. Mexican authorities detained the director and four guards over that clash. Surveillance video showed two inmates opening doors to let armed prisoners into a room where the slain victims were reportedly holding a party.
Twenty-three people were killed in a prison riot in Durango city in 2010, and a 2009 riot in Gomez Palacio, another city in the northern Mexican state of Durango, killed 19 people.
Associated Press
