A five-storey apartment building collapsed late on Monday in western India, killing one person, with at least 70 feared trapped.
The number of missing people is probably between 51 and 200, local officials said.
There were 47 flats in the collapsed building, said police in the town of Mahad, 120 kilometres south of Mumbai in Maharashtra state.
The cause of the accident was not immediately clear, but such incidents are common during India's monsoon season, with old and rickety structures brought down by heavy rain.
The death toll from global monsoon-related disasters this year has topped 1,200, including more than 800 in India.
Three rescue teams with sniffer dogs were sent to the scene, India's National Disaster Response Force said.
Home Minister Amit Shah said he was "praying for everyone's safety".
Emergency workers retrieved the body of one victim, response force spokesman Sachidanand Gawade said.
Fifteen injured people were rescued and taken to hospital, police said.
Residents and police combed through tin sheets and other wreckage in a desperate search for survivors as ambulances ferried victims to nearby hospitals.
About 70 people fled to safety when the building began to buckle, Nidhi Choudhari, an official in the district, told PTI.
Ms Choudhari said the situation could have been worse if many families living there had not returned to their villages because of the coronavirus lockdown.
Local politician Manik Motiram Jagtap told TV9 Marathi that the building was 10 years old and built on "weak" foundations.
"It fell like a house of cards," Mr Jagtap said. "It is a scary situation."
As night fell, emergency workers used cranes to remove the debris as relatives anxiously waited for news of their loved ones.
Uddhav Thackeray, the state's Chief Minister, had been in touch with local representatives, his office said on Twitter.
"He has assured them that all possible support will be extended for speedy rescue and relief works," a spokesman said.
Maharashtra has been hit hard by the coronavirus pandemic, accounting for over a fifth of India's more than three million infections.