"The bus was headed towards Ahmednagar," District Disaster Control Officer Jaideep Visave said. (Agencies)
The injured are being rushed to hospitals at Murbad and Tokawade.
According to unconfirmed reports, the mishap occurred when driver of the bus lost control while negotiating a sharp turn.
"The district headquarters got the message around 10:30 am and a team comprising police personnel, medical attendants and rescue workers was rushed to the spot. The number of casualties is not known immediately as the spot of the mishap lies deep into the valley," Visave said.
Malshej Ghat is a famous picnic spot located in the Sahyadri mountain range, situated on the border of Thane and Ahmednagar districts.
Many ambulances were rushed to the spot for shifting the injured, police said.
Meanwhile, MSRTC GM (traffic) Suryakant Ambawdekar said that erratic network coverage was hampering communication with officials at the spot.
"As per initial information available with me, a truck collided with the bus knocking it off into the valley," he said.
"The bus was headed towards Ahmednagar," District Disaster Control Officer Jaideep Visave said.