Heavy monsoon rains in western India caused at least three walls to collapse on to huts and city shanties, killing at least 27 people and injuring dozens of others, officials said on Tuesday, as forecasters warned of more rain.
At least 18 people were killed and 66 others injured when a 10-metre wall demarcating an urban forest collapsed during the night in Mumbai, police officer Sunil Deshmukh, said.
Rescue teams with sniffer dogs were searching the area afterward, and Indian Navy teams fanned out to help rescue residents of the waterlogged city, India's financial and entertainment capital.
Nine deaths were caused by two wall collapses elsewhere in Maharashtra state.
Six migrant construction workers were killed and five injured when a wall collapsed on their tin-roofed huts in Pune on Tuesday, an officer in the city's Police Control Room said.
In Thane district, the wall of a school collapsed and fell on to huts, killing three people and injuring one, Lakshman Pawar, a local civic official said.
The monsoon season in India brings heavy rains from June to September that cause flooding and other damage. Building collapses are common as the rains weaken the foundations of poorly built structures. On Saturday, another wall collapse in Pune killed 16 people living in a cluster of tin-roofed huts housing migrant workers and their families.
Monday's rains also flooded roads in Mumbai and covered train tracks.
India's Central Railway said in a tweet that "nature's fury" made operating trains a "safety hazard" in some areas. Trains were running at partial service on Tuesday after thousands of passengers were stranded overnight.
Millions of passengers commute daily on a network of famed railways in Mumbai.
There has been incessant rainfall in the city over the past few days and floodwaters have entered homes. A public holiday was declared for Tuesday and the Maharashtra government said only emergency services would be functional.
Maharashtra chief minister Devendra Fadnavis tweeted: "People are advised to stay indoors unless there is any emergency."
Weather officials said Mumbai received the highest rainfall in a decade over a two-day period since Sunday. TV channels showed videos of submerged cars and water flowing through ground floors of some residential buildings.
A plane on a domestic flight skidded off the main runway at the Mumbai airport on Monday night, and flight operations were partially restored on Tuesday. At least 50 domestic and international flights were diverted and 50 other flights were cancelled.