16 people have been taken to a nearby hospital, with five of them said to be critically injured
At least 11 people have died and around 20 others are feared trapped under the rubble of a building which collapsed following heavy rain in Mumbai.
The multistorey Hussain building in the south of the city had 11 families living in it when it collapsed.
"A 43-member team is conducting rescue operations," an official for India's National Disaster Response Force (NDRF) told AFP.
A play school was also functioning in one of the rooms of the building but it is not clear how many children were attending the school when the structure collapsed.
Emergency services and the NDRF personnel are carrying out a search and rescue operation and ambulances have taken 16 people to the nearby JJ Hospital - five of them are critically injured.
"As the incident happened at 8.30 in the morning there is the possibility of more people trapped inside," an NDRF official said.
South Mumbai has more than 16,000 buildings built before the 1940s and the Brihanmumbai Municipal Corporation (BMC) identified 791 of these buildings as dangerous in its pre-monsoon survey.
Locals have told reporters that the Hussain building was about 50 years old, however it is not clear if the building was classified as dangerous.
The structure also damaged surrounding houses as it fell on adjoining buildings.
At least 15 people have died over the last two days due to the severe rain and floods in the city.
Buildings in the financial capital are often constructed hastily and illegally, and flawed building plans are sometimes approved by bribes.
Mumbai is India's most densely populated city, home to more than 24 million people, and has the most expensive real estate.
Population pressure coupled with land scarcity and insufficient public housing forces people into illegal and unsafe tenements.
Last month 17 people died in Mumbai when a four-storey building collapsed. Illegal renovations were taking place on a nursing home on the ground floor of the building.
In 2013 an under construction and illegal building collapsed killing 74 people in Thane on the outskirts of Mumbai. The building was home to at least 150 people.