Another 60 people are still feared trapped under the debris of Huseini Building, which came crashing down with a huge booming sound around 8.25 a.m.
War-like efforts were on to rescue those trapped, a BMC Disaster Control official said, adding the death toll could increase.
Twenty persons were rescued from the rubble within three hours of the incident, he added.
The building is situated in a heavily congested locality of south Mumbai’s C Ward, and rescue teams with their big vehicles and heavy equipment faced a tough time approaching the crash site.
The injured, that included two firemen, were rushed to hospital.
According to a woman, the building also housed a nursery-cum-playschool. The playschool was scheduled to open at 10 a.m., two hours after the building collapse.
Local residents, mainly Dawoodi Bohra community members and others, initiated their own manual rescue efforts, moving the rubble with their hands to help the victims.
A 90-strong team of NDRF, State disaster management, a 150-strong team of fire brigade personnel and workers, two sniffer dog squads, electronic gadgetry along with five fire engines, two JCBs, one crane and other machines were deployed to rescue the people buried under the massive heap of rubble.
A BMC bulletin at noon said the structure included an uninhabited godown on the ground floor and total 10 tenements on the remaining upper floors.
It added that the building – a Maharashtra Housing and Area Development Authority (MHADA) cessed structure – was part of the Saifee Burhani Upliftment Trust (SBUT) redevelopment project, and declared unsafe for living at least six years ago.
“The dangerous building was served evacuation notice in 2011 and the occupants ordered to vacate it to make way for the SBUT redevelopment project, but they failed to heed the warnings,” said a BMC official.
According to the Fire Brigade, the building’s two wings have completely collapsed. The cause of the crash is being probed.
This is the first major building collapse after Tuesday’s deluge in Mumbai, and the second in five days after the Chandivali Crystal Business Park crash on August 26, that claimed six lives.