Brazilian officials say at least 52 people have been killed, including 35 police and prison guards, during a series of attacks by an organized crime group.
Authorities blamed the gang (called First Command of the Capital) for ordering the attacks in response to the transfer of several imprisoned gang leaders to maximum security facilities.
They say gang members used machine guns, grenades and home-made bombs in 100 attacks on police stations and other sites across Sao Paulo state beginning Friday. Police say they detained 16 suspected attackers and killed 14 others.
Meanwhile, inmates took hostages in 36 prisons in the state to protest the prisoner transfer.
Officials said late Saturday that they had regained control of several prisons, but new disturbances were reported Sunday at 18 facilities.
Brazilian authorities say jailed gang leaders often direct gang activity, including arms and drug trafficking and prison rebellions.
Some information for this report provided by AP, Reuters and AFP.