Heavy rains in Brazil's southern Rio Grande do Sul state have killed at least 10 people and left 21 missing since Monday, the country's civil defense said Wednesday.
An additional 11 people were injured and more than 3,300 were forced to leave their homes due to damage caused by the storms, the civil defense added.
Operators reported electricity and water cuts across the state, and officials detailed numerous incidents of flooded roads, landslides and collapsed bridges as water levels of rivers and streams rose sharply.
Authorities activated the Brazilian Air Force to assist stranded people. It deployed two helicopters for the rescue mission.
The southern state's crisis Cabinet met on Wednesday. Rescuing people in isolated and island areas is the priority, vice-governor Gabriel Souza said, according to a statement. Authorities had registered more than 130 rescue requests by Wednesday morning.
“There is a special concern with dams in an alert situation, with risk of failure and flooding due to very high levels,” Souza added. Residents in nearby areas are being relocated, he said.
The downpour started Monday and was expected to last through Friday, civil defense authorities said.
In some areas, such as valleys, mountain slopes and cities, more than 150 millimeters (6 inches) of rain fell in 24 hours, said Brazil's National Institute of Meteorology, known by the Portuguese acronym INMET, on Tuesday.
Weather across South America is affected by the climate phenomenon El Niño, a periodic naturally occurring event that warms surface waters in the Equatorial Pacific region. In Brazil, El Niño has historically caused droughts in the north and intense rainfall in the south.
This year, the impacts of El Niño have been particularly dramatic, with a historic drought in the Amazon. Scientists say extreme weather is happening more frequently due to human-caused climate change.
