The two Maharashtra state transport buses were carrying 18 passengers, two drivers and two conductors.
Maharashtra Chief Minister
"There were two parallel bridges; one is a new bridge and one constructed during the British era. The old one collapsed,” he said.
“The primary reason seems to be the high pressure caused due to flooding of river Savitri due to heavy rains in catchment of Mahabaleshwar,” said Fadnavis.
Meanwhile, the state administration rushed to the spot for rescue operations and traffic on the highway has been stopped.
Prime Minister Narendra Modi spoke to Fadnavis today and was briefed about the bridge collapse.
"The PM offered all help in rescue and relief operations," Fadnavis said.
NDRF teams are already activated, he tweeted.
The Coast Guard has deployed a Chetak helicopter to carry out search for people who were swept away from the bridge.
Soon after the incident, Raigad SP Suvez Haque and Collector visited the spot where the bridge once stood.
Darkness had hampered operations, which resumed this morning.