At least 94 people have died from floods and mudslides that swept away homes in the Brazilian mountain town of Petropolis.
It was still not known how many people were trapped under the debris more than 24 hours after the disastrous deluge.
"We don't yet know the full scale of this. It was a hard day, a difficult day," Rubens Bomtempo, mayor of the "Imperial City", said at a news conference on Wednesday.
Rio de Janeiro's public prosecutor’s office said it had compiled a list of 35 people yet to be located as families dug through the mud to find their loved ones.
Nearly 400 firefighters have been deployed to search for the missing, local media reported.
Petropolis, named for a former Brazilian emperor, was ravaged by incessant rainfall on Tuesday, that exceeded the average for the entire month of February.
Videos surfacing on social media showed houses are cars being washed away and water swirling through the city. On Wednesday morning, houses were left buried beneath the mud.
According to the state fire department, 25.8cm of rain fell within three hours on Tuesday. Claudio Castro, the governor of Rio de Janeiro, said that the rains were the worst Petropolis has received since 1932.
"No one could predict rain as hard as this," Mr Castro said, adding that nearly 400 people were left homeless and 24 people were recovered alive.
"The situation is almost like war ... Cars hanging from poles, cars overturned, lots of mud and water still," the governor added.
According to officials, at least 80 houses were hit by landslides in the Morro da Oficina area.
"I lost my niece and her five-year-old daughter, who we still haven't found. We did not expect this tragedy. Our city is over," Hilda, a distraught resident, whose house had been damaged due to the rains, told Reuters.
Shopkeeper Henrique Pereira said the water came "very fast and with great force" causing him a great loss. "Our life was already tough with the pandemic and less movement, and this tragedy still comes," he added.
More rain is expected through the rest of the week, according to weather forecasters. Petropolis' city hall has declared three days of mourning.
Brazil's president Jair Bolsonaro, who is on a trip to Russia amid the bilateral tensions in eastern Europe, expressed solidarity on Twitter.
"We intend to already offer to the mayor what we can," Mr Bolsonaro told reporters in Moscow, adding that he would release federal funds to help "restore traffic in the region".
Heavy rains have triggered deadly floods in northeastern Brazil and Sao Paulo since December last year. Over 40 deaths have been recorded between incidents in Minas Gerais state in early January and Sao Paulo state later the same month.
