Twenty-five prisoners have died in Brazil after fellow inmates set fire to mattresses in a cell during a dawn riot, police say.
Officers said the incident appeared to be a settling of scores between rival gangs in the Ponte Nova jail in the central state of Minas Gerais.
Brazil is notorious for its overcrowded prisons and the presence of organised criminal gangs within their walls.
There have been several mass prison riots in recent years.
The Ponte Nova detention centre, 180km (110 miles) south-east of the regional capital Belo Horizonte, has about 175 inmates living in a space meant for 87.
The fire occurred after a group of prisoners broke out of one section of the jail and entered another wing, officials told AFP news agency.
They surrounded a rival gang and set their mattresses on fire, gutting the top floor of the wing.
Police broke up the riot using water cannon and tear gas. The remaining inmates were rounded up.
Officials said no-one had escaped from the jail during the fire.
Medical teams are trying to identify the bodies.
The blaze came days after President Luis Inacio Lula da Silva announced a $3.3bn (£1.7bn) package of measures aimed at reducing violence, which include building 160 new prisons and expanding social programmes.
The new jails are expected to have special facilities to provide job training and education.
But the BBC's Gary Duffy in Sao Paulo says that, given the scale of the problem, the measures seem unlikely to resolve the issue of overcrowding.