By Marilia Brocchetto, Fernando Ramos and Ray Sanchez CNN

(CNN) -- Mudslides killed more than 150 people and injured many others after heavy rains caused rivers to overflow late Friday night in Colombia's Putumayo province, authorities said.

Many residents have been reported missing, according to the civil protection authorities and President Juan Manuel Santos' office.

"We don't know how many (deaths) they'll be," Santos told reporters at the scene. "We continue to search."

The president later confirmed 154 deaths in a broadcast aired on local TV channel Cable Noticias.

"Unfortunately, it is possible that the number of deaths will go up because we have a lot of missing people," Santos said. "We don't know yet where they are. Many people are coming to us saying, 'My son is missing, my father is missing, my mother is missing.' We are working on putting a list for the total number of people missing."

At least 190 people were injured, and firefighters are searching for survivors, said a Twitter post from the country's fire service.

Photos released by Colombia's military showed rescuers carrying old women and children over downed, mud-caked trees and homes.

Santos said 130 millimeters, or more than 5 inches, of rain fell in the area Friday night, setting off the deadly torrents. The monthly average is about 400 millimeters, or about 16 inches, he said.

"Here we are facing a disaster caused by nature, by climate change," Santos said.

Santos has declared a state of emergency.

Electrical power and water were out in Mocoa, and the hospital system was shut down, according to firefighters.

Heavy rains battered the southwestern region of the country on Friday.

Three rivers in the area, including the Mocoa and San Boyaco, overflowed and unleashed muddy waves into homes, over cars and onto bridges, according to Mocoa Mayor José Antonio Castro, CNN en Español reported.

In 2015, torrential rains in northwest Colombia caused a landslide that killed more than 80 people as mud rushed into homes and bridges, officials said.

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