About 250 families had to abandon their homes due to a fire of unknown origin that spread on Tuesday across several city blocks in Paraisopolis, a shantytown here in Brazil's largest city, authorities said.

The blaze, which left no known casualties, began about 4 a.m. and spread rapidly through the rickety houses jammed into the poor neighborhood given that many of them are made of highly flammable material, the Sao Paulo fire department said.

Firefighters brought the fire under control within five hours, but not before about 100 homes were damaged or destroyed.

The number of people made homeless by the fire is almost 300, given that several of the structures that were damaged had two or three floors.

Authorities said that this week they will perform an evaluation of the affected houses to determine which are unfit for habitation and will have to be demolished and which can be reoccupied.

Fire department Maj. Roberto Lago, who headed the operation, said that the task was made more difficult by the significant slope of the local terrain where the houses were located and due to the abandoned vehicles and the large quantity of trash in the vicinity, all of which hindered access by fire trucks. EFE