NEW DELHI - In one of the worst single traffic accidents in ?India, at least 51 people were killed and 46 others injured when an overloaded bus rolled into a 90-meter-deep gorge in the northern Indian state of Himachal Pradesh on Saturday, police said.

The private bus was heading for Chamba town when it skidded off the road and fell into the gorge near Rajera, some 10 km from the town and around 475 km from the state capital Shimla.

The 40-seater bus was overcrowded with about 100 people, some of whom were even sitting on its roof, said police.

While 39 passengers died on the spot, 12 others died on the way to hospital.

Witnesses said the bus driver lost control while negotiating a turn.

The road condition could have been made worse by heavy rains over the past few days in the remote mountainous area.

Local residents tried to save the passengers from the wreckage before the authorities reached the spot.

Himachal Pradesh Chief Minister Prem Kumar Dhumal and leader of opposition Vidya Stokes expressed grief over the accident.

The state government has launched probe into the accident.

Police blame buses belonging to private operators and their " reckless, untrained drivers" for most of the fatal accidents in the state.