Two buses carrying at least 22 people plunged into a fast-flowing river in western India after a bridge collapsed following days of torrential monsoon rains, officials said Wednesday.

Rescuers raced to the crumbled bridge south of the financial capital of Mumbai to search for the passengers swept away following the accident late on Tuesday night.

Television footage showed large chunks of the British-colonial era bridge had fallen into the rain-swollen Savitri 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.

The bridge straddling the river lies along a major highway connecting Mumbai to the tourism state of Goa.

Emergency workers armed with diving and other specialist equipment were scouring the river for the missing, but no one has been rescued so far, India's disaster management chief told AFP.

"As per initial information, some vehicles and people have been swept away. Our team has rushed to the spot," National Disaster Response Force chief O.P Singh said.

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

Television footage showed a helicopter flying over the river searching for survivors.

Maharashtra Chief Minister Devendra Fadnavis said the bridge appeared to have collapsed after being pounded by the flooded river.

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

The incident is the latest in a string of deadly accidents in India where enforcement of safety rules is weak and substandard materials are often used.

In April, an under-construction flyover collapsed in the eastern city of Kolkata, killing 26 people.

Scores of people die every year from flooding and landslides during the annual monsoon rains in India and the neighbouring countries of Nepal and Bangladesh.

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