Sickening footage from a Brazil prison where 57 prisoners were killed in riots appears to show inmates playing football with decapitated heads.
In the stomach-churning video around six inmates are seen on the roof of the Altamira prison during the five hour long outbreak of violence.
Images also show piles of severed heads lying on the floor.
Two rival factions have been blamed for starting the troubles, with one group breaking into an area housing their rival, locking the room and setting fire to it.
Para state prison authorities said 16 of the dead were beheaded and the other were asphyxiated in the riot at the prison in northern Brazil.
Two prison officers who were taken hostage have been freed.
The death toll could rise after authorities have searched all areas involved, state prisons chief Jarbas Vasconcelos said at a news conference.
Other footage on Brazilian media showed smoke billowing from at least one prison building, while another clip had inmates walking on the rooftops.
Authorities have not named the two rival gangs involved.
The prison has a capacity of 200 but was occupied by 311 prisoners.
Jarbas Vasconcelos, state prisons chief in Brazil, said the fire spread rapidly, with inmates held in old container units that had been adapted for the prison while another building is under construction.
“It was a targeted attack,” Mr Vasconcelos said. “The aim was to show that it was a settling of accounts between the two groups, not a protest or rebellion against the prison system.”
Prison authorities said they were still trying to determine who were the leaders behind the attack, and those men will be transferred to federal prisons.
No guns were found during the riot only makeshift knives.
The killings mirrored those of 55 inmates who died in a series of riots in May in several prisons in the neighbouring state of Amazonas.
President Jair Bolsonaro was elected on the promise of curbing widespread violence in Brazil, including in the country’s often overcrowded, out-of-control prisons.
According to a report from the National Justice Council, the prison has 343 detainees despite having a maximum capacity of 163.
In early 2017, more than 120 inmates died in prisons across several northern states when rival gangs clashed over control of drug-trafficking routes in the region.
The violence lasted several weeks, spreading to various states.
Prison authorities said they had not received any prior intelligence reports of an upcoming attack.