At least 57 prisoners were killed, according to Altamira prison officials cited in media, after clashes broke out between rival criminal groups in the detention facility in Brazil’s northern Para state on Monday.

Footage shows family members of prisoners gathered near the detention centre. Weapons allegedly used in the attack can also be seen, piled on a truck.

Comando Classe A criminal group reportedly set on fire a cell with Comando Vermelho inmates thus preventing police forces from entering the building for several hours.

According to official statement, 16 victims were found decapitated.

At least 46 inmates are expected to be put in other prisons, with 10 more to go into other detention centres with stricter conditions.

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