The cause of the collapse of the building, where employees of the Municipal Corporation of Greater Mumbai were housed with their families, was still not known.
But police said on Saturday they had arrested a man identified by the municipal authority as having leased a part of the basement and done some construction that may have changed the structure of the building, which was built in the early 1980s.
A spokesperson for the city authority said so far 50 people had been confirmed dead and 32 people injured from Friday's collapse.
A shortage of cheap homes in Indian cities has led to a rise in illegal construction, often using substandard materials and shoddy methods.
In April, a building collapse killed 72 people in Thane, just outside Mumbai. Officials had said that the structure was built with poor materials and did not have proper approvals.
Several diggers had been pressed into action to lift some of the larger slabs of concrete, allowing teams of rescuers wielding heavy equipment to take out bodies and search for those still alive.
The Municipal Corporation of Greater Mumbai said Friday that some of its employees and their families were housed in the structure and had been asked to leave earlier this year.
"The building was around 30 years old. We had issued a notice to them in April, to vacate the building, but they did not act," spokesperson Vijay Khabale-Patil said.
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