Media captionInmates were seen on the rooftop of the prison during the violence

Conditions at a prison in Brazil where 57 inmates were killed in fighting on Monday have been described as "terrible" in an official report.

The National Justice Council said that Altamira jail in north-eastern Pará state contained more than double the number of inmates it was built for.

It also said that there were not enough guards to guarantee inmates' safety.

Deadly fights are not uncommon in Brazil, which has the world's third-largest prison population.

What happened?

The violence broke out at 07:00 local time (10:00 GMT) on Monday when members of a criminal gang housed in Block A of the jail, invaded an annex where members of a rival gang were locked up.

Sixteen inmates were decapitated in the fight which followed. Many more died from smoke asphyxiation after the fighting prisoners set a cell on fire.

Video taken from outside the prison showed smoke billowing from the building and inmates walking around on rooftops.

The inmates also took two prison officers hostage but released them after negotiations with civil and military police.

The fighting lasted for about five hours.