Jarbas Vasconcelos, Superintendent of the Para Penitentiary System, said 16 of the 52 inmates who died in Altamira Prison were beheaded.
The remainder is said to have died of suffocation because the prisoners had set fire to part of the facility, reported the state news agency Agencia Brasil.
The uprising started when a group of prisoners stormed a rival-controlled prison wing, Agencia Brasil reported, citing a statement by Para State Prison authorities.
Two correctional officers were released months.
The local prison authorities at the time stated that the deaths were due to violent clashes between rival factions within the same drug gang. known as the family of the north.