An abandoned building occupied by squatters in São Paulo has caught fire and collapsed, sending fiery debris crashing into neighbouring buildings and surrounding streets, Brazilian officials say.
Firefighters said at least one person had been killed in the collapse and that there could be more.
The building, a former headquarters of the federal police, caught fire around 1:30am local time.
Firefighters set up a perimeter and worked to evacuate people.
A few hours later, as flames engulfed the building of at least 20 stories, it collapsed.
Globo TV, which was covering the fire, captured the destruction. Images showed the floors falling in on themselves and debris flying in all directions.
Romulo de Souza, 49, said he was part of a squatter occupation in the neighbouring building. He said that when the fire began on the fourth floor of the former police headquarters, families began evacuating.
"Happily the majority got out," he said.
Mr de Souza said that residents believed the fire could have been started by a gas leak.
Firefighter Lt Andre Elias told Globo TV that at least one person had been killed in the collapse.
Authorities were working to locate several others who were missing.
The fire and collapse will put a spotlight on occupations in Sao Paulo, South America's largest city.
Several dozen buildings have been occupied in the city centre by highly organised fair-housing groups that take over and then fight for ownership.
Many such dwellings are run like regular apartment buildings, with doormen and residents paying monthly fees and utility bills. Others are less established and more precarious.