Mudslides have killed 112 people, injured 180 and left up to 200 missing after destroying homes in southern Colombia, the Red Cross and officials said Saturday.
The surge swept away houses, bridges, vehicles and trees, leaving piles of wrecked timber and brown mud, army photographs from the town of Mocoa showed.
The mudslides struck late Friday after days of torrential rain.
President Juan Manuel Santos visited Mocoa, the capital of Putumayo department, on Saturday to supervise rescue and assistance efforts in the heavily forested region.
"I have just been informed that 112 people are dead," he said. "We don't know how many more there will be; we are still searching."
Earlier, the Red Cross aid group's rescue official Cesar Urena told AFP that 92 people were dead and 180 injured.
He warned that the death toll -- initially put at 16 -- would probably rise further because 200 people were still missing.
"The number is rising enormously and at considerable speed," he said.
The disaster is of "large proportions," he added.
Putumayo Governor Sorrel Aroca called the development "an unprecedented tragedy" for the area.
There are "hundreds of families we have not yet found and whole neighborhoods have disappeared," he told W Radio.
Carlos Ivan Marquez, director of the National Disaster Risk Management Unit, told AFP the mudslides were caused by the rise of the Mocoa River and tributaries.
The rivers flooded, causing a "big avalanche," the army said in a statement.
Some 130 millimeters (5 inches) of rain fell Friday night, Santos said. "That means 30 percent of monthly rainfall fell last night, which precipitated a sudden rise of several rivers," he said.
He promised earlier on Twitter to "guarantee assistance to the victims of this tragedy, which has Colombians in mourning."
"Our prayers are with the victims and those affected," he added.
The authorities activated a crisis group including more than 100 local officials, military personnel, police and rescuers to search for missing people and begin removing mountains of debris, Marquez said.
Mocoa, a town of 40,000 people, was left without power or running water.
"There are lots of people in the streets, lots of people displaced and many houses have collapsed," retired Mocoa resident Hernando Rodriguez, 69, said by telephone.
"People do not know what to do... there were no preparations" made for such a disaster, he said.
"We are just scarcely realizing what has happened to us."
Several deadly landslides have struck Colombia in recent months.
A landslide in November killed nine people in the southwestern rural town of El Tambo, officials said at the time.
A landslide the month before killed 10 people in the north of the country.