The bus carrying about 40 persons was on its way from Reckong Peo in Kinnaur to Nauni in Solan. According to police, the toll is expected to rise.
Rescue operations are in full swing and SDM Mithun Jindal and DSP Deva Singh Negi are on the spot.
The injured have been admitted to the civil hospital at Khaneri, Shimla District Commissioner Rohan Chand Thakur said.
So far 15 bodies have been recovered, police said.
The NDRF has been rushed to the spot to supervise relief and rescue operations.