The Thane-Diveagar bus went off the road on Ghonse ghat, apparently as the driver lost control of the vehicle, and fell into the valley near Karegaon village in Mhasala taluka at around 11.30 am, Mhasala police said.
The dead include driver Dhananjay Chavan and conductor of the bus Balasaheb Narawade, the police said.
Chief Minister Vilasrao Deshmukh announced compensation of Rs 1 lakh each for the families of the deceased.
The bus, carrying around 50 passengers, had started its journey from Thane at 6.30 am.
Union Minister A R Antulay (who hails from Raigad district), state Guardian Minister Sunil Tatkare, and Minister of State (PWD) Ravisheth Patil visited the spot later in the day.
Names of the passengers who died in the mishap: Meghana Thosar, Liyakat Ulde, Mayuresh Joshi, Ramesh Warankar, Irfan Bandarkar, Mahadeo Sutar, Vijay Karkhanis, Atharva Ketkar, Devangi Thosar, Sakharam Nivankar, Vedant Kulkarni, Arun
Kambale, Waman Kate, Kishor Mahadik, Omkesh Welaskar, Ganesh Warankar, Maiuddin Ulde, Khatija Ulde.
Body of one male passenger is yet to be identified.
Photograph: Chandrakant Goregaonkar