Nearly 22 people went missing after a bridge across a fast-flowing river on the Mumbai-Goa highway in India collapsed late on Tuesday night.

Officials said almost 80 per cent of the bridge across the Savitri River has collapsed and two Mumbai-bound buses and a dozen other vehicles are believed to have fallen into the flooded river.

Television footage showed huge chunks of the British-colonial era bridge had fallen into the river.

"Twenty two people from two buses are missing after the 50-feet (15-metre long) bridge collapsed," Sanjay Patil, police superintendent of Raigad district where the accident occurred, told AFP.

Three teams of the National Disaster Response Force (NDRF), comprising of about 80 personnel including divers, rushed to the spot and started their rescue operations but the process is slowing down due to heavy rainfall in the area.

"As per initial information, some vehicles and people have been swept away," National Disaster Response Force chief O.P Singh said.

"Our team is equipped with deep divers and life-saving equipment," he added.

The police said they are also using the Navy and Coast Guard helicopters to spot possible survivors. But no survivors or vehicles have been found so far.

Maharashtra Chief Minister Devendra Fadnavis said the bridge appeared to have collapsed due to torrential monsoon rains and floods.

"The primary reason seems to be the high pressure caused due to flooding of river Savitri due to heavy rains in the catchment of Mahabaleshwar," he said on Twitter.

The bridge was about 5 km from the town of Mahad in Maharashtra's Raigad District, about 170 km south of Mumbai.