Conflicting reports emerged from the Jardinopolis Penitentiary, northwest of Brazil's biggest city, after the incident.
The state prison service confirmed in a statement that there had been a riot, but said "prisoners who escaped were recaptured" and taken to another facility.
However, Globo's G1 news site reported that of some 200 inmates who broke out, only 100 had been so far recaptured.
Footage broadcast on Globo television showed smoke pouring from the Jardinopolis prison. Footage also showed a large section of prison fencing knocked down to the ground.
Like many prisons in Brazil, Jardinopolis is heavily overcrowded, with a population of 1,864 but a capacity of only 1,080, according to the state penitentiary service.
Riots and mass escape attempts are common across Brazil, Latin America's biggest economy.