At least 52 people have died during a prison riot in the northern Brazilian state of Para, BBC reports.

The state’s prison authority has said the violence involved five hours of battle between two rival gangs, one of which invaded another wing in the Altamira jail. During a news conference, officials said 16 victims were decapitated during the onslaught. Additional news reports have indicated the prison was set on fire, asphyxiating many inmates. 

During the violence, which reportedly began around 7 a.m. local time and didn't end until noon, two prison officers were taken hostage. Military officers were brought in to negotiate with the inmates, who had barricaded themselves in a cell block, per the Daily Mail.

Video footage uploaded to Twitter shows part of the facility engulfed in flames, and other graphic scenes from the violence. According to Brazilian outlet G1, the Altamira prison has a capacity of 200, but 311 inmates were being held there. 

The riot on Monday arrives months after 55 people were confirmed dead in gang-related prison riots in the neighboring state of Amazonas in May. The violence reportedly involved rival factions within the same drug gang, known as the Family of the North. 

Brazil has the third-highest prison population in the world, and overcrowding in prisons is a widespread issue. Similarly to Monday's attack, the prisons where inmates were killed in May was well over capacity. Many have blamed the far-right Brazilian government for increased violence in prisons, which often function as recruiting centers for gangs.