Seven inmates died amid unrest at a prison in the eastern Mexico state of Veracruz, authorities said Sunday, with 11 other prisoners suffering injuries.
The fighting first broke out Saturday afternoon at a facility in Tuxpan and continued throughout the night, officials said.
Veracruz state forces, along with military support, carried out a "coordinated operation" and were able to get into the prison by Sunday morning and regain control, said a statement from the state security ministry.
"As a result of the riot, we report the tragic deaths of seven inmates and 11 injured people," the statement said.
After the fight, three inmates were transferred to another prison in Veracruz, though authorities did not disclose specifics.
Local media reported that the prisoners started the riot after asking authorities to guarantee their safety when faced with threats from inmates who were accused of being part of a violent criminal group called Sombra.
Conflicts between cartels and other organized crime groups in Mexico are often replicated in prison populations, which struggle with overcrowding.
Last month, a prison riot in the northwestern state of Sinaloa left three inmates dead.
Politicians have also been targeted by violence in Veracruz in recent months. In May, a mayoral candidate and three of her supporters were shot dead at a campaign event in the state. Last December, a Mexican congressman who was a member of the ruling coalition was shot dead in Veracruz.