At least 60 people have been killed, with many getting beheaded, after a 17-hour prison riot broke out on Sunday afternoon in the Amazon jungle city of Manaus in Brazil.

"This is the biggest prison massacre in our state's history," Sergio Fontes, the public security secretary of the state, said, adding that many of the victims were decapitated and suffered a lot of violence.

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Authorities have recovered 60 bodies so far, and all of them are inmates. Officials are also trying to determine whether any prisoners have escaped.

Authorities believe that the riot was initiated by rival groups, which have been fighting for drug trafficking control inside and outside the prison, the BBC noted.

The riot eventually came to an end after the inmates agreed to free the last of the 12 prison staff they were holding hostage. Fontes noted that the inmates had "almost no demands" during negotiations, as they only requested not to be transferred or to be mistreated by police authorities and to maintain their visitation privileges.

The massacre last Sunday is the latest violent clash between members of the First Capital Command drug, which is one of the biggest gangs in Brazil, and a local powerful group known as the Family of the North.

TagsBrazil, prison, Drugs