At least 20 prisoners died early Thursday morning after inmates broke out of their cellblock and set a fire, apparently attempting to settle scores with a rival gang, Brazilian media reported, according to AP. The prisoners who died could not escape from their cellblock after their attackers set fire to mattresses at the lockup in the town of Ponte Nova in the south-central Brazilian state of Minas Gerais, according to the Web site of Globo TV. A spokesman for Minas Gerais state did not immediately return a phone message seeking comment, and telephones to police rang busy. Globo and the Estado de Minas newspaper reported that authorities put out the fire, but at least 20 prisoners died and authorities were trying to identify them. The rest of the prisoners were rounded up in a patio of the lockup. Prison conditions are often criticized as horrendous in Brazil, and gangs frequently rule the lockups. The Ponte Nova prison had capacity for 87 inmates, but 187 inmates were being kept there, Globo said.