The bus, which was carrying over 100 passengers – many of them on the roof – veered off the road in a sparsely populated and hilly area of the state of Himachal Pradesh.
“Fifty-two people have been killed and 45 injured in the accident,” Sunil Chaudhary, district deputy commissioner, told AFP, adding the death toll could rise because at least a dozen of the injured were in a critical condition.
There were anguished scenes as families came to claim the bodies of the victims. Many of the dead had boarded the 42-seater bus when their own bus broke down, locals told AFP.
Some of the bodies were taken away by their families for cremation while the state government brought in four truckloads of wood to cremate other victims at the accident site.
The cause was not immediately known but some witnesses said that the driver lost control of the vehicle on a sharp bend.
The accident occurred in the morning near Chamba town, about 190 kilometres (120 miles) from the state capital Shimla. The area where the accident happened is treacherous and known for zig-zag turns.
Villagers were the first to reach the accident site and frantically struggled to pull the dead and injured from the twisted wreckage. Later, emergency crews arrived, covering the dead in white sheets.
The bus had been on its way to Chamba from Dulera when it flew off the road. Thirty-nine people were killed instantly while the others died on the way to hospital, Chaudhary said.
It was the second major bus tragedy in a week, in a country where road accidents with dozens dead at a time are common.
On Wednesday, 31 people were killed when their bus tumbled into a gorge in Meghalaya state, in India’s remote northeast.
In 2008, some 63 bus passengers returning from a religious celebration were killed when a burst tyre ignited the vehicle’s fuel tank east of the Taj Mahal city of Agra.
India has the highest annual road death toll in the world, according to a 2009 World Health Organization report, with accidents caused by speeding, careless driving and treacherous roads.
Himachal Pradesh’s Chief Minister Prem Kumar Dhumal offered his “heartfelt condolences to the families of the dead” and said the next of kin would get 100,000 rupees ($1,800) from the government.
“The state government has ordered an inquiry into the accident,” Dhumal said.
The Chamba district borders Indian Kashmir and has been lashed by heavy monsoon rains in the past few days.