A 15ft (4.5m) high wall collapsed on a cluster of tin-roofed huts housing migrant workers and their families in western India early on Saturday following heavy rain.
At least 16 people were killed, an official said.
The wall dividing the car parking area of a multi-storey residential apartment building collapsed in Pune, a city in Maharashtra state, fire official J Gaekwad said.
Three people were pulled out of the rubble alive and taken to hospital, he added.
The wall collapsed as the city was deluged by 2.8in (7.3cm) of rain on Friday, the second-highest rainfall for the month of June in the past nine years, the Press Trust of India news agency said.
The workers and their families were sleeping when the wall collapsed on them.
The victims were migrants from eastern Bihar state and northern Uttar Pradesh state. The migration of workers from these impoverished states to other places in India is common because of lack of job opportunities.
Bimal Sharma, who survived with minor injuries, said he escaped as some trees blocked the stones and vehicles that came down toward the huts, according to the Hindustan Times newspaper.
He shouted for help and was rescued by people living nearby. He lost his younger brother in the collapse, the newspaper reported.
The workers were employed at an adjacent construction site. The rescue and clearing operation was completed after nearly nine hours, Mr Gaekwad added.
Separately, three people were electrocuted in Mumbai, India’s financial and entertainment capital, as delayed monsoon rains hit Maharashtra state on Friday, the Times of India newspaper reported.
Building collapses are common in India during the June-September monsoon season, when heavy rains weaken the foundations of structures that are poorly constructed.
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