At least 57 prisoners were killed by other inmates during clashes between organised crime groups at the Altamira prison in northern Brazil on Monday, according to prison officials.
Para state prison authorities said 16 of the victims were decapitated while others suffocated after the prison buildings were set on fire.
The count of victims could rise when authorities have searched all areas involved, state prisons chief Jarbas Vasconcelos said at a news conference.
Vasconcelos said a fight between criminal groups at the Altamira prison erupted around in the morning, when breakfast was being served.
A group of prisoners reportedly tried to take over another part of the prison complex.
Inmates also set fires and roadblocks that prevented authorities from entering parts of the facility for about five hours, he said.
Brazilian officials said that the government is investigating the attack.
The killings echoed those of 55 inmates who died in a series of riots in May in several prisons in the neighbouring state of Amazonas.
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.
Brazil has the world’s third-largest prison population, with 726,712 inmates as of June 2016, according to official statistics.
The population is double the capacity of the nation’s prisons, which in the same year was estimated to be 368,049 inmates.
Along with severe overcrowding, Brazil’s prisons are plagued by gang violence, while riots and breakout attempts are not uncommon.-AL JAZEERA