Thirty-two people were injured, including four critically, and the search continues for rescuing a few more people who remain trapped under the debris, said the BMC Disaster Control department.
Among the victims in the tragedy was 31-year journalist with Sakal newspaper, Yogesh Pawar, and his father Anant Pawar, a civic employee.
Situated near the Dockyard Road, south Mumbai, the 33-year-old building served as civic employees' staff quarters.
Housing around 21 families, it suddenly collapsed around 5.45 a.m. Friday, catching majority of the sleeping residents unawares, the official added.
Moving to fix responsibility for the state's second worst building crash tragedy of this year, Mumbai police arrested the proprietor of a marquee decoration firm who had allegedly carried out illegal modifications on the ground floor of the doomed building.
Suspected renovation and alterations carried out in his office-cum-warehouse may have led to further weakening of the dilapidated structure and hastened its collapse.
On a complaint by a civic official, Sewree police nabbed Ashokkumar J. Mehta of Mamamiya Decorators under various charges pertaining to culpable homicide not amounting to murder, according to Additional Police Commissionner (South) Krishna Prakash.
Image: Rescue workers dig through the rubble at the site.