Fire brigade and police personnel rushed to the spot and started a rescue operation.
At least three people were killed and six others injured when a two-storey under-construction structure in a chawl collapsed on Sunday morning, the police said.
The incident took place at around 9.15 am at Motilal Nagar in Goregaon (West) when the slab of the two-storeyed building gave way during construction, an official said.
The structure was part of a chawl (tenement) of the Maharashtra Housing and Area Development Authority (Mhada), he said.
Fire brigade and police personnel rushed to the spot and started a rescue operation, he said.
At least three fire engines, one rescue van and an ambulance were deployed for the operation, the official said.
At least nine people trapped inside the debris were rescued and rushed to Siddharth Hospital in Goregaon, he said.
A 27-year-old man, Shravan Kumar Goremandal, was declared dead on arrival, he said.
One Subhash Chavan, 38, and an unidentified person also died soon after, the official said.
Three of the injured, Mangal Bansa, 35, Munna Shaikh, 30, and Shekhar, 35, were admitted in the hospital, while the others were discharged after treatment, he said.
An accidental death report was registered at the Goregaon Police station and a probe is underway, he said.