The incident triggered by intense rains left at least 65 people injured in Mocoa, a city of 350,000 people located near Colombia's border with Ecuador.
Carlos Ivan Marquez with Colombia's national disaster agency says the river flooded around midnight, catching unsuspecting residents off guard in the early hours today.
Emergency response workers were continuing the search for survivors, with the number of reported deaths climbing in the morning hours.
Images shared by residents online showed vast areas filled with wood planks and other debris.
Disclaimer: No Business Standard Journalist was involved in creation of this content