The bus, which was carrying about 40 people, was attempting to cross a shallow river when it was hit by sudden flash floods.

Eighteen people were rescued when they formed a human chain and waded through the stiff river current with the help of ropes while another five, including the bus driver and conductor, swam to safety.

According to the driver, 15 people were killed. But the conductor put the death toll at between 30 and 35, senior police official Prem Kumar Thakur told

There was no official confirmation of the death toll.

"The operation to rescue the alive persons has ended, but we have yet to decide whether the missing persons will be hunted in the waters now or at daylight," another official said.

"We have not yet recovered any bodies so far and cannot tell about the exact number of dead and missing," he added.

Heavy rains in the higher hills triggered of the flash floods in the Sarsa river.

According to reports reaching here a large number of people have gathered at the sight, mostly as curious onlookers.

Heavy machinery such as cranes and search lights were brought in from the nearby city of Chandigarh, some 50 kilometres (31 miles) away.

The Sirsa river was continuing to rise, gradually submerging the bus in the Nalagarh area of Solan district, 90 kilometres (56 miles) west of Shimla, capital of Himachal Pradesh state.

"The river is around 500 feet (152 metres) wide. Normally, it is shallow enough for and buses to cross it but today there were sudden flash floods which trapped this bus," Thakur said.

TERRA.WIRE