At least seven persons were killed and 12 injured when a bus skidded off the road and rolled down the hill in Sirmaur district in Himachal Pradesh on Sunday, an official said.The private bus was on its way from Manva to Solan town when the accident occurred near the Nai Neti panchayat, around 25 km from Rajgarh town.Most of the injured have been admitted to the Regional Hospital in Solan, about 55 km from the state capital.Sirmaur Deputy Commissioner Lalit Jain told IANS the rescue operation was over. Most of the victims were from Rajgarh area.He said the cause of the accident was yet to be ascertained.Eyewitnesses said the administration had a tough time extricating the victims from the badly mangled bus.People in the area began rescue operations even before authorities reached the spot.