The inmates at the Amazonas jail were choked to death or stabbed with toothbrushes, Colonel Marcos Vinicius Almeida, head of the state’s jails, said in the statement.
The riot began during visiting hours. There were no hostages and violence was directed between inmates, Almeida said.
The jail was the scene of an inmate uprising that ended with 56 dead in 2017.
The government will investigate the cause of the riot, the statement said.
Meanwhile, on Sunday, there were pro-government rallies in at least 156 cities, according to news website G1.
Those in the streets on Sunday argued that Brazil’s political system has not allowed right-wing President Jair Bolsonaro to push through his legislative agenda and make progress in critical areas like security, education and the economy. They say that Bolsonaro is standing by his core pledge to not engage in the traditional political horse trading in Brasilia that is largely blamed for stunning levels of corruption in the nation’s political class.
Bolsonaro initially considered participating in the demonstrations, before deciding against it and recommending the government’s ministers not to join. Rhetoric from some organizers challenging the authority of Congress and the Supreme Court also turned off members of the president’s party and other allies.