At least 25 prisoners died early Thursday in Brazil after inmates broke out of a cellblock and set a fire in an apparent attempt to settle scores with a rival gang, a police official said.

The victims could not escape their cellblock after the attackers set fire to mattresses before dawn in the prison in Ponte Nova, a town in south-central Brazil, said Lt. Andrea Amara Lopes.

Authorities put out the fire and rounded up the rest of the inmates while they tried to identify the victims and the perpetrators.

Human rights activists often criticize Brazil for having horrendous conditions in prisons, where gangs frequently rule the lockups. The Ponte Nova prison had capacity for 87 inmates, but 187 were being kept there, according to the website of the Estado de Minas newspaper.

One of Brazil's worst cases of prison violence came in May 2006, when a powerful prison-based gang launched attacks on Sao Paulo's streets and inside prisons that prompted a week of bloodshed.

The gang initially targeted police officers — shooting them on the streets, at stations and in their homes — leaving 41 dead.

Nearly 200 people in all were killed, among them prison guards, suspected criminals, jail inmates and bystanders. More attacks in July 2006 left six people dead and human rights advocates alleged that police seeking revenge killed innocent victims.

Thursday's fire came two days after Brazil's president, Luiz Inacio Lula da Silva, said his government will invest nearly $3.3 billion US for new prisons and social programs in the next five years to reduce prison-based violence that often spills outside.

Brazil's Justice Ministry plans to construct 160 prisons, give scholarships for police officers and expand social programs in poor areas where crime is rising, such as in Sao Paulo and Rio de Janeiro.

The new prisons will each be able to house 400 inmates, and educational opportunities will be offered to some of the nation's 420,000 prisoners.