Heavy rains overnight caused several rivers to overflow, sending mud and sediment onto homes and roads in the provincial capital of Mocoa, which has around 100,000 inhabitants.
"It is a very critical situation," Carlos Ivan Marquez, the head of the country's disaster response team told Caracol Radio. "Between 14 and 16 people have been reported dead, among them various minors and some adults who are in the process of being identified."
A witness told the radio station he fled his house in the middle of the night because of the rising river. Cellphone videos showed residents searching for survivors in the debris of destroyed buildings.
"It's a big area," Mocoa Mayor Jose Antonio Castro also told Caracol. "A big portion of the many houses were just taken by the avalanche, but above all the people were warned with enough time and they were able to get out, but houses in 17 neighborhoods have basically been erased."
Two bridges were also destroyed, Castro said, and there was an indeterminate number of people missing.
"The figures have been going up and in the crisis room they kept reporting more dead, we hope to God that (the death toll) will not go up too much because it is very sad."
Colombian President Juan Manuel Santos will visit the area, the government said. Santos said via Twitter that he was praying for the victims and had ordered immediate help for Mocoa. Heavy rains and a mountainous landscape regularly cause landslides in the Andean country.
(Reporting by Nelson Bocanegra, writing by Julia Symmes Cobb; editing by Jeremy Gaunt, G Crosse)
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