At least 57 people have been killed in a prison riot in Brazil which saw rival gangs battle for five hours, officials say.
Gang members from 1 prison block invaded another part of Altamira prison in Pará state.
Sixteen of the dead were decapitated and the rest suffocated after a part of the prison had been set on fire, officials said at a news conference.
Two prison officers who were taken hostage have been freed.
The violence started at about 07:00 local time (10:00 GMT) on Monday, and finished at about noon, officials said.
Members of the Comando Classe A (CCA) gang set fire to a cell in which rival gang members from Comando Vermelho (Red Command) were retained, the Pará state authorities said in a statement.
The arrangement of the cell allowed the fire to spread rapidly, leading to the death by asphyxiation of some offenders.
Officials said that both prison officers taken hostage were soon released since the objective of the attack was to strike in the rival gang – instead of in the prison guards.
There was no prior warning or indications of an impending attack on this scale, the announcement said.
Video reported to be from the prison conducted by Brazilian media showed smoke billowing from at least one prison construction, while another clip seemed to reveal offenders walking around on the rooftops.
The prison in Altamira where Monday’s violence broke out has a capacity of 200 but was inhabited by 309 prisoners. Officials denied that it was overcrowded.
