Over 50 prisoners were reported killed during a prison riot Monday between rival gangs at Altamira prison in Brazil's northern Para state.

Prison authorities said a fight broke out around 7 a.m. local time (10:00 UTC). Inmates belonging to a local gang known as Comando Classe A set fire to a part of the prison occupied by the rival Rio de Janeiro-based gang Comando Vermelho, or "Red Command."

Read more: Several killed in Brazil prison gang battle, dozens escape

Many of the victims reportedly died of smoke inhalation, as the fire prevented police from entering the building for several hours, the state prison chief said in a statement. Two guards were also held hostage, but were eventually freed. 

Officials said that 16 prisoners were decapitated, and that only makeshift knives were found on the scene after the riot.

According to numbers obtained by Agence France Presse, some 311 prisoners were being held at the jail, and it reportedly has a capacity for 200 inmates. Officials say it wasn't overcrowded. 

Read more: Inmates beheaded in prison riot in southern Brazil

Brazil's Ministry of Justice and Public Security said those responsible for the violence would be transferred to federal jails, which are more secure.

"It was a targeted act," state prison director Jarbas Vasconcelos said in a statement, adding that their officials had no intelligence indicating a clash was imminent. 

"The aim was to show that it was a settling of accounts between the two gangs."

The deadly riot in a prison at Altamira is the latest unrest in Brazil's notoriously overcrowded jails. Brazilian President Jair Bolsonaro had promised to take measures to stop widespread violence in Brazil's prison system. 

Read more: Brazil struggles through President Jair Bolsonaro's first six months

In May, at least 55 prisoners were killed in several jails the neighboring Brazilian state of Amazonas, in gang clashes over an apparent drug trafficking dispute. 

Read more: Brazil: 42 inmates found dead in Amazonas prisons

According to the latest official statistics released this month, Brazil had more than 720,000 inmates as of June 2017, which is the world's third-largest prison population after the US and China. 

wmr, jsi/jm (AFP, AP, Reuters)

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