A landslide in Colombia's south-western border province of Putumayo sent mud and debris crashing onto houses, killing 127 people and injuring at least 400.
Heavy rains caused several rivers to overflow, pushing sediment and rocks onto buildings and roads in the provincial capital of Mocoa and immobilising cars in several feet of mud.
The Red Cross reports that 127 people are dead, 220 missing and 400 injured.
President Juan Manuel Santos arrived in Mocoa to assess the damaage and and declared a state of emergency.
"We have sent a team of 150 people to make our response effective and machinery began work immediately," Carlos Ivan Marquez, head of the disaster unit, said.
Photos posted on Twitter by the air force showed neighbourhood streets filled with mud and damaged houses while videos on social media showed residents searching for survivors in the debris and struggling to move through waist-high water overnight.
"It's a big area," Mocoa Mayor Jose Antonio Castro said on Saturday.
"A big portion of the many houses were just taken by the avalanche, above all people were warned with enough time and they were able to get out, but houses in 17 neighbourhoods have basically been erased."
A combination of heavy rains, a mountainous landscape and informal construction of homes makes landslides in the Andean country relatively common.