Dozens of rescuers were clearing the debris to find any residents possibly still trapped at the New Collector complex in Malad West, the Brihanmumbai Municipal Corporation told Asian News International.
Maharashtra Minister Aslam Shaikh blamed the heavy rains for the building collapses, the source cited.
With the onset of the monsoon rains in the Indian state of Maharashtra, the heavy downpour disrupted life with several landslide incidents, collapse of walls and bridges in the city of Thane and the neighboring districts of Palghar.
The flood hit Mumbai and paralyzed the city, interrupting local train services after causing flooding in several parts.
Mumbai recorded 222 millimeters (8 inches) of rain in 12 hours. Tidal waves that reached up to 4. 6 meters (13 feet) prevented the rainfall from being drained, and roads, rail tracks and neighborhoods were left waterlogged.