Twelve bodies have so far been recovered and the bus has been pulled out of the water, Bilaspur Deputy Commissioner Ajay Sharma said, adding that a search is on for those missing.
The exact number of passengers travelling on the bus is not known. The ill-fated bus belonging to a private transportation company was on its way from Rishikesh to Bilaspur and most of the passengers were locals.
The 40-seater bus was packed to capacity and some passengers were also said to have been travelling on its roof, sparking fears that the toll may rise.
About half-a-dozen people who sustained injuries as they jumped off the bus in a bid to save themselves have been taken to a hospital in Bilaspur.
A large crowd of locals has gathered at the spot making anxious enquiries about relatives.