The death toll from the collapse of a five-storey apartment block in Mumbai climbed to 50 on Saturday and was expected to rise as more than a dozen people were feared trapped in the rubble.
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 spokesman 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.