The mishap occurred at around five pm when the bus, which had come from Dhulia was heading to Vasai, Deputy Superintendent of Police (Ganeshpuri) Vishal Thakur told PTI.
Prima facie, the driver lost control over the vehicle and hit the parapet wall of the bridge, after which it fell into the river, the officer said, adding police personnel were rushed to the spot.
Around 25 persons, who were travelling in the bus, sustained injuries, he said, adding they have been admitted to nearby hospitals.