Twenty three bodies have been recovered so far from the accident site, a police official told PTI over phone.
The cause of the accident is being ascertained.
The incident took place when the bus heading towards Dhangadhi from Doti fell around 200 metres down the hilly road at Chhatiwan village development area in Doti district, some 700-kilometre west of Kathmandu, the police said.
The deceased have not been identified yet.
Police, Army and local people have been mobilised for carrying out rescue and relief works, local authorities said.