The state fire department said more than 180 soldiers were working in the stricken Petropolis region, which got 25.8 centimetres (more than 10 inches) of rain within three hours on Tuesday – almost as much as during the previous 30 days combined.
Footage posted on social media showed cars and houses being dragged away by landslides and water swirling through the city of Petropolis and neighbouring districts.
Petropolis’s city hall said in a statement the heavy rains left “a high number of incidents and victims” and that rescue and recovery efforts were under way.
Brazilian President Jair Bolsonaro, who is on a trip to Russia, said on Twitter he had instructed the government to deliver immediate support to the afflicted.
“May God comfort the family members of the victims,” he wrote.