The Public Safety Department said the prison had been brought back under control. Zacatecas state security secretary Ismael Camberos Hernández told the Milenio television station that inmates angry over the Tuesday riot had attacked prisoners they accused of betraying them that day.
He said the prisoner had been battered to death by fellow prisoners who detached a metal cell door and bashed him with it. The four wounded Thursday also suffered injuries from blows. But in Tuesday's riot, authorities confiscated four guns that they believe were smuggled in during visiting hours. Prison guards were placed under investigation after the riot.
Not all of the victims in Tuesday's riot died from gunshot wounds. Some were stabbed and others beaten with objects. No guards or police were wounded. Local media reported the prison held members of various gangs and cartels, including the Sinaloa cartel and the Gulf and Northeast cartels.
Such killings frequently involve score settling between rival cartel members or a battle for control of the prison's illicit business. Mexico has a long history of deadly prison clashes. In October, six inmates were killed in a prison in Morelos state.
In September, Nuevo Leon state closed the infamous Topo Chico prison, the site of many murders over the years. In February 2016, 49 prisoners died there during rioting when two factions of the Zetas cartel clashed.