"It is with sadness that I have to announce that so far 27 people, including three minors, have lost their lives in the tragedy," writes the president on Twitter.
The landslide occurred on Sunday, trapping people inside a bus and other vehicles as the road was submerged in mud.
A survivor says that the bus driver managed to back away from the worst of the landslide.
The ongoing rainy season, which began in August, is Colombia's worst in 40 years, according to the government.