Authorities in the Brazilian state of São Paulo say at least 36 people have been killed in heavy flooding and landslides, forcing some cities to cancel annual Carnival celebrations, the BBC reports.
Rescue teams have been struggling to reach survivors and unblock roads.
More than 600mm of rain fell in some areas on Sunday, twice the expected amount for the month.
“Search and rescue teams are not managing to get to several places; it is a chaotic situation,” said Felipe Augusto, the mayor of the hard-hit town of São Sebastião.
“We have not yet gauged the scale of the damage. We are trying to rescue the victims.”
Dozens were missing in the town and about 50 houses had collapsed and washed away, Mr Augusto added, saying that the situation remained “extremely critical”.
The state government reported at least 35 deaths in São Sebastião and the mayor of Ubatuba, some 80km north-east, said a young girl had been killed. Hundreds have been displaced and evacuated.