Bali said that two Himachal Road Transport Corporation buses - both from Manali - were trapped under boulders.
One of the buses was carrying 47 passengers from Chamba to Mandi while the second bus, was carrying about 8-10 passengers from Katra to Manali when the accident occurred.
A Home Ministry official said that as many as seven teams of National Disaster Response Force (NDRF), comprising 45 personnel in each, have already reached the affected areas in Bihar. Those injured were immediately rushed to the nearby hospital.
The coaches had stopped for a tea break around midnight yesterday in Himachal Pradesh when tonnes of rock and mud swept away an entire stretch of highway roughly 200 kilometres from the state capital Shimla.
Local TV channels reported that the two buses were stationed at a roadside eatery located on the highway for refreshments when the disaster occurred.
A more than 150 metre stretch of the road was washed away in the mudslide. Rescue operation has been under way since 2am, he said, adding, one bus was going to Chamba while another to Katra from Manali when the incident took place. Three of the eight persons on the bus died. They believe 35-50 passengers were on the bus at the time of the incident. "As per estimates, 25-30 are missing", an official told IANS.
Chief minister Virbhadra Singh visited the accident site and announced Rs. 5 lakh ex gratia to the kin of those who lost their lives in the accident.