The accident occurred around 10.30 a.m. when the Thane-Ahmednagar bus belonging to Maharashtra State Road Transport Corporation (MSRTC) went off the road and plunged into the narrow gorge.
According to preliminary investigations, the bus driver lost control of vehicle at a steep curve on the treacherous ghat roads, and the bus with 45 passengers fell into the ravine, an officer of the Thane rural police said.
Helped by local villagers, police and fire brigade personnel from Thane and Pune are engaged in the rescue operations which are hampered by the steep mountain slopes.
Several wounded people were rushed to hospitals in Murbad and Thane. The toll is likely to go up, police said.