Carlos Ivan Marquez, the director of the national disaster agency, told the AFP news agency that a crisis group, including military units, police and rescue teams, had been activated to search for the missing people, as well as begin removing hundreds of tons of debris. He suspected the death toll would rise.
"In the middle of the night and this morning people lost loved ones", Minister of Interior Juan Fernando Cristo said.
The slides washed away power stations, knocking out half of the electricity in the department of Putumayo, where Mocoa is located.
"Under the mud, I am sure there are many more", he said Saturday after working throughout the night on patients.
The rainfall total in one night amounted to almost half the precipitation the city of Mocoa typically receives in the entire month of March, he said, adding that local and national authorities must work to prevent another tragedy as the rainy season gets underway.
Cars were overturned and seen hanging part way out of buildings, whilst two bridges were destroyed, authorities said. With the rainy season in much of Colombia just beginning, he said local and national authorities need to redouble their efforts to prevent a similar tragedy. Santos said via Twitter that he was praying for the victims and had ordered immediate help for Mocoa.
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The incident happened around midnight, as many residents were in their homes sleeping.
A statement released by the Columbian government states that the Columbian President Santos is on his way to the area.
President Juan Manuel Santos is expected to visit the region Saturday. The incident triggered by intense rains left at least 125 people dead.
The torrential rains triggered what the Colombian Army called an "avalanche" of muddy and debris strewn water from the Mocoa River and its tributaries.
Herman Granados, a surgeon at the local hospital, said he believed there are likely more than 300 people injured and that doctors were quickly running out of blood.