The landslide, caused by strong rains, hit the vehicle between the villages of Pueblo Rico and Santa Cecilia in Risaralda province, about 230km (140 miles) from the capital Bogota.
"We have already found 33 people dead, including three minors, and we have rescued nine people alive, four of them are in critical condition," Interior Minister Alfonso Prada told reporters on Monday.
Colombia's President Gustavo Petro described the incident as a tragedy in a Twitter message.
Con tristeza debo anunciar que hasta el momento 27 personas, incluyendo 3 menores, han perdido su vida en la tragedia de Pueblo Rico, Risaralda. Solidaridad con las familias de las víctimas, tendrán un acompañamiento integral por parte del Gobierno Nacional.— Gustavo Petro (@petrogustavo) December 5, 2022
"Solidarity with the families of the victims," he added, pledging support from the national government.
Pueblo Rico Mayor Leonardo Fabio Siagama told reporters that bodies were being brought to a covered stadium in the town that is normally used for sports.
Rescue workers are still searching the scene for others
Risaralda's governor, Victor Manuel Tamayo, said earlier that five people had been rescued alive from the bus.
Officials had said at least 25 people were on the bus traveling between Cali, Colombia's third largest city, and Condoto, in Choco province.
Colombia had been hit by an unusually heavy rainy season, blamed on the La Nina weather phenomenon,
Events linked to heavy rains have killed more than 216 people and left 538,000 homeless so far in 2022, according to government statistics. Another 48 people are still missing across the country, the figures show.