RIO DE JANEIRO -- Authorities in Brazil say two inmates have been killed in a riot that erupted in an overcrowded southeastern prison.

Rifle-toting police were seen firing against apparently armed prisoners who were holding fellow inmates hostage on the roof of the penitentiary in Governador Valadares city.

Social defence secretary Bernardo Santana told media Sunday that inmates also started a blaze by setting fire to some mattresses. Images from TV stations were showing prisoners with orange uniforms wrapped around their faces holding a knife on a man's neck before throwing him about 20 feet from the roof.

The 290-bed prison was housing more than 820 inmates when the uprising began Saturday. Riots often break out across Brazil over harrowing conditions at congested jails where many detainees haven't been convicted.