A major portion of the fourth floor of the building, which was being repaired, at Nakhuda Mohalla on Narayan Dhuru Street collapsed on Friday.
While the building had been vacated, a restaurant, Burhani, was being run on the ground floor of the building on top of which the other floors came crashing.
Kamal Siddique Shaikh, 25, Balleshwar Mahanto, 26, and Imitiaz Abdul Siddiqui, 28, were declared dead on Friday. Mohammad Shaikh, 26, is under treatment.
Locals said a huge amount of construction material was piled up on the fourth floor, the weight of which the building could not withstand.