At least 55 people have died in prison riots in Manaus, Brazil, since Sunday in a prison complex notorious for overcrowding and extreme violence.

The first riot broke out on Sunday during visiting hours at the Anísio Jobim penitentiary in Manaus, Amazonas state, between rival factions within the same drug gang known as the Family of the North (FDN). According to a statement from prison authorities, 15 inmates were killed during the clashes by being choked to death or stabbed with toothbrushes.

Col. Marcus Vinicius, in charge of prisons in Amazonas, denied reports that the rioting was a rebellion, describing it as a “fight among inmates.” He added that prison violence was inevitable but that this incident broke the unwritten prison rule of “never killing during a family visit.”

“We have to have the maturity to understand that, in any prison in the world, when someone wants to kill, they will kill,” he said. The ringleaders of the gangs involved have since been transferred to separate facilities.

The clashes continued on Monday, killing 40 prisoners across four facilities in Manaus, all apparently of asphyxiation. The mother of one inmate described the violence as “total chaos.”

“Everyone started to run, and everyone was pounding on the cell gates, at the doors, and running down the corridors,” she said, according to the BBC.

Amazonas Gov. Wilson Lima told reporters that the Justice Ministry had agreed to send a “prison intervention team” to the state to help restore order.

“I just spoke to Justice Minister Sergio Moro and he is already sending a prison intervention team to the state of Amazonas to help us in the critical moment with a problem that is national: the problem with the prisons,” Lima said.

The clashes will present another challenge to President Jair Bolsonaro, elected last year on a promise of restoring peace and security to a country where violence is widespread. His plan to fulfill that pledge included recommending the construction of more jails and empowering local authorities to tighten control of the facilities.

The issue of prison riots has long been a major problem in Brazil. The last major spate of riots in 2017 killed over 100 people. Many of the deceased were subject to brutal violence, including the ripping out of hearts and intestines and multiple decapitations.

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