"Among the dead is Mr (Byron) Lima," who was convicted for his role in the 1998 murder of Juan Gerardi, and died during a "brawl" among inmates, Interior Minister Francisco Rivas told reporters. A previous toll had just two dead.
The clash took place yesterday inside Pavon prison, just outside the capital, after authorities tossed a grenade at the inmate's "security detail."
Rivas said the deadly uprising was linked to Guatemalan drug lord Marvin Montiel Marin, alias "El Taquero," who has been in the same prison for the 2008 killings of 15 Nicaraguans and a Dutch national.
Lima was serving a 20-year prison sentence handed down in 2001. Three others, including his father, a former colonel, were convicted over the bishop's murder.
While serving his sentence, Lima was considered one of the most powerful figures inside Guatemala's prison system.
In 2014, a judge charged Lima with leading a criminal network that effectively controlled prison life, including arranging inmate transfers, conjugal visits and access to phones.