Sixteen prisoners were decapitated and dozens more also died in a mass prison riot in Brazil.
At least 52 inmates were killed in the latest in a series of deadly clashes involving rival criminal gangs in the northern state of Para.
The gangs took at least two officers hostage as they battled one another.
Other prisoners were asphyxiated, and the total number of victims could rise, authorities said.
Inmates also set part of the Altamira prison on fire, preventing guards from entering parts of the building.
Brazil’s jail population has surged eight-fold in three decades to around 750,000 inmates – the world’s third-highest tally - and its prison gangs have come to wield vast power that reaches far beyond prison walls.
His ability to curtail violence, however, may be limited because most prisons are controlled at the state level.
In January 2017, nearly 150 prisoners died during three weeks of violence in several prisons as local gangs backed by Brazil’s two largest drug factions attacked one another.
Gruesome deaths are not uncommon. In May, at least 15 inmates were found dead, choked to death or stabbed with toothbrushes in the city of Manaus.
Additional reporting by agencies