Nearly 400 people have been injured and 200 people are still missing, the army statement added, as search and rescue efforts continue in the city of Mocoa located in the department of Putumayo.
Three rivers near the city of 45,000 people burst their banks Saturday amid torrential rain, creating an avalanche of water and mud that washed up all its 17 districts.
The disaster has affected more than 500 families in the area, leveling dozens of homes, according to the Colombian Red Cross.
In the early hours of Sunday, the military were able to restore partial land access on the highway to Mocoa. The town remains without electricity and fresh water.
Putumayo Governor Sorrel Aroca said the event was "an unprecedented tragedy.
“There are hundreds of families we have not yet found and whole neighborhoods have disappeared," he said in an interview on W Radio.
President Juan Manuel Santos on Sunday was to pay a second visit to the heavily forested disaster zone to oversee search efforts.
The president is enlisting further Air Force missions to “transfer out the injured and bring in rescue teams”, he said on his Twitter account.
A senior UN official in Colombia, Martin Santiago said in a statement Sunday: “The nature and magnitude of this event, the catastrophe and tragedy is tremendous.”