Some 111 prisoners were killed and 17 police officers were injured in a riot at a Sao Paulo prison, a state security official said Saturday.
The uprising broke out Friday afternoon when rival gangs in the House of Detention's Pavilion 9, which houses some 2,500 inmates, attacked each other with homemade knives and clubs in the patio.
The conflict quickly spread into a general riot, with prisoners setting fire to mattresses and doors.
Prison officials called in military police, riot squads with helicopters and firefighters, spokesmen said.
The uprising was put down in about four hours after police exchanged gunfire with inmates and lobbed teargas cannisters into the pavilion.
Valmir Salaro, a spokesman with the Public Security Secretariate of the Sao Paulo State government, said he did not know how many police took part in the action.
The House of Detention prison was built to hold a maximum of 3,500 prisoners. There are currently 7,350 inmates there, from first-time offenders to maximum-security prisoners.
The institution, called in the local press "the powder keg," has a history of violence.
In March 1982, 14 prisoners died in a similar uprising. In 1985, 3,200 inmates took over the prison for 20 hours before officials finally got it under control. Nine inmates died.