One of drug lord El Chapo's biggest rivals has been killed in a prison riot that left six dead.
Two other inmates were also injured in the clash in Atlacholoaya prison, in the central Mexican state of Morelos.
Pictures emerged of prison guards being taken hostage and forced to lie on the ground with their hands on their heads.
Some are seen facing the wall and kneeling for cover.
Inmate, meanwhile, wore masks and brandished metal poles as they took control of the federal prison.
The national guard, federal and state police were sent to the scene after receiving reports of the emergency situation.
The Morelos state interior secretary said officers re-established the control of the facility a few hours after they took down six prisoners.
Raymundo Isidro, also known as El Ray, who is considered the leader of the Cartel Jalisco Nueva Generacion in Morelo, was among those who were killed, according to a statement issued by the authorities.
"Some 350 security personnel were deployed for the implementation of the national security protocols, and full and total control (of the prison) was regained," it added.
The other victims were identified by the names of Jose Manuel, Roberto, Lorenzo, Vicente and Nestor, who were reported as dead, and the two injured prisoners were named as Leopoldo and Adalberto.
Uriel Carmona, the prosecutor of the state, said that the inmates were killed due to the use of blades and denied firearms were used.
It is unclear who killed the victims.
Pablo Ojeda, the Secretary of Government of Morelos, said that a day before the riot another fight had taken place between inmates over stolen shoes.
One inmate was killed and a further two injured in the fight, meaning seven prisoners were killed in the prison in 24 hours.
A video shows dozens of prisoners gathered during the riot as guards can be seen running away.
Another clip shows relatives of inmates demanding information from cops outside the prison.
There are no updates on the condition of the injured inmates.
