The riot happened Sunday at a prison in Manaus, the capital of Amazonas state, said the head of the state’s prisons administration, Pedro Florencio.
“There are 60 dead so far,” he told journalists.
Riots are common in Brazil’s overcrowded and underfunded prisons.
Some 622,000 people were imprisoned in Brazil as of the end of 2014, according to a justice ministry report. Most of them are black males.
That makes it the world’s fourth-largest prison population, the report said, after the US, China and Russia.
Human rights groups have long complained about the conditions in Brazilian prisons.
On October 18, deadly riots broke out at three separate prisons blamed on fighting between members of the country’s two largest gangs.
During that episode, rioting inmates took visitors hostage, beheaded rivals and burned others alive, authorities said.