The building, Banoo Apartments, opposite the busy railway station, was 15-years old.
Over 100 people managed to escape before it crashed, said a police official in Mumbra, around 30 km from Mumbai.
An hour before it collapsed, there were indications of the impending disaster as the building started shaking and wobbling.
A majority of the panicky residents chose to evacuate and moved to safety.
At least three people are feared trapped under the debris and efforts are on to rescue them.
This is the sixth major building collapse in Mumbai and its neighbouring areas in the past six months.
In April, a building collapsed in Lucky Compound in Mumbra, killing 75, and making it the worst such disaster in the state's history.
In June, four more buildings crashed in Mahim (10 dead), Mumbra (10 dead), Dahisar (seven dead) and Bhiwandi (three dead).