Floods and landslides triggered by heavy rain have killed 36 people in Sao Paulo, and officials expect the death toll to grow.
The governor of Sao Paulo said on Sunday that 35 people died in Sao Sebastiao, and a 7-year-old girl was slain in neighbouring Ubatuba.
The municipalities of Sao Sebastio, Ubatuba, Ilhabela, and Bertioga were the most severely affected by the floods and landslides.
When rescue personnel attempted to locate injured persons and bodies in the rubble of collapsed buildings, carnival celebrations were cancelled in the towns.
"Our rescue personnel are unable to reach multiple areas. As stated by the mayor of São Sebastio, Felipe Augusto, it is a chaotic situation.
As a result of the landslides, he later reported that dozens of people were missing and 50 homes had collapsed in the city.
Mr Augusto shared other images on social media depicting widespread wreckage in his community, including a baby being saved by strangers on a flooded street.
Monday, President Luiz Inacio Lula da Silva of Brazil will visit the region, he announced on Twitter.
The government of Sao Paulo said that rainfall in the region had exceeded 600 millimetres in a single day, one of the biggest amounts of rain that Brazil has experienced in such a short period.
According to the state authorities, Bertioga received 687 millimetres of precipitation within that time.
The army responded to Governor Tarcisio de Freitas' call for assistance by dispatching two aircraft and rescue crews to the region.
Only the roofs were visible in television images of flooded homes.
People use small boats to transport themselves and their belongings to higher land. Landslides and flooding obstructed a road connecting Rio de Janeiro with the port city of Santos.
The northern coast of Sao Paulo is a popular Carnival destination for affluent tourists who wish to avoid city street festivities.