Police had initially believed that 34 passengers were on the bus and were searching for three missing people earlier Sunday.

"We initially thought there were 34 passengers according to a list including two drivers but it seems some people cancelled at the last minute," said TC Palonkar at the Raigad district police control room.

The bus had been carrying 31 passengers when it skidded off the road and plunged 150 metres into a gorge in the Western Ghats mountain range in Maharashtra state on Saturday.

"Only one passenger managed to escape as the bus fell. He was the one who informed the police," Palonkar said.

The bus was carrying employees of an agricultural university in the town of Dapoli to the hill station of Mahabaleshwar for the weekend. The group was on an annual outing.

The front window of the bus broke as it fell, and the lone survivor, Prakash Sawant-Desai, caught hold of the branches of a tree through it. He later climbed down the tree and clambered up the steep slope, Palonkar said.

"I managed to climb up and called up Dr Balasaheb Sawant Konkan Agriculture University authorities and the police," Sawant-Desai, an assistant director at the university, was quoted as saying by IANS.

Rescue operations, which have now ended, were difficult as it was raining intermittently and the area is forested.

A team from the National Disaster Response Force and trekking club members from nearby towns, along with local villagers, helped with the operations, Palonkar added.

Australian Associated Press