The accident occurred in the wee hours on Friday when a bus skidded off the road at Salanghat area of Rorang rural municipality and fell 200 meters below into Trishuli river.
Three bodies recovered from accident site and two from other places.
Sixteen people injured in the accident rescued by Nepal Police and Army personnel and admitted in local hospital.
Later nine injured were referred to Kathmandu for further treatment.
According to reports around 40 people were travelling in the ill fated bus which was heading towards Kathmandu from Sarlahi district.
Search operation for missing passengers is underway.