At least 29 inmates were killed as rival gangs clashed inside a prison in a cartel-plagued Mexican state, authorities said. Three policemen guarding the prison were wounded.
In one attack, 20 inmates were shot to death when a group of prisoners opened fire on members of a rival gang inside the prison in Mazatlan, Sinaloa, state Public Safety Secretary Josefina Garcia told Radio Formula.
One of the three wounded police was in serious condition, Ms Garcia said.
The gang that initiated the attack killed 17 rivals and lost three of its own members.
An inmate who was wounded died later at a hospital, said Martin Gastelum, a spokesman for the Sinaloa state prosecutors' office. He didn't say which gang the prisoner belong to.
The lockup in the Pacific coast city of Mazatlan was quickly brought under control and investigators found two pistols and an assault rifle inside, Mr Gastelum said.
Mr Gastelum said the killings were all at the hands of other prisoners.
Local media said those attacked were apparently members of the Zetas drug gang, which is battling the powerful Sinaloa cartel, but officials were unable to confirm that.
Hours later, eight more prisoners were stabbed to death by other inmates, said state Public Safety Department spokeswoman Angeles Moreno. She said police are investigating what sparked the violence.
Many of Mexico's most powerful drug traffickers hail from Sinaloa, a key smuggling corridor and cultivation area for marijuana and opiates. The northwestern state, and Mazatlan in particular, are rife with turf battles among drug gangs.
Mexico's drug gangs frequently try to break their members out of prison, by staging attacks from the outside or buying off prison officials. But there was no immediate confirmation that the shootings involved a prison-break attempt.Reuse content