NEW DELHI — At least 31 people were killed when torrential rain swept through India"s financial capital late on Sunday, triggering landslides that crushed cars and houses while leaving neighborhoods devastated. Twenty-one people died in the Mumbai suburb of Chembur, in India"s western state of Maharashtra, while 10 people were killed in the suburb of Vikhroli, according to Satya Pradhan, India"s National Disaster Response Force director-general. Rescue efforts continued through the night, with workers digging through mud and debris to find survivors. Mumbai"s water supply was also affected after a purification complex flooded, the city"s municipal corporation said on Twitter. It added that thunderstorms and "extremely heavy rainfall" would continue in isolated places. Indian Prime Minister Narendra Modi offered his condolences to the families of those killed. "Saddened by the loss of lives due to wall collapses in Chembur and Vikhroli in Mumbai," Modi wrote on Twitter. "In this hour of grief, my thoughts are with the bereaved families." In the 24 hours ending Monday morning local time, Mumbai airport recorded more than 250 millimeters (9.8 inches) of rainfall, according to data analyzed by CNN Weather. Mumbai, a city of 12 million people, regularly experiences heavy rainfall during the July-September monsoon season. The rain often triggers building collapses — especially in poorer districts known to house illegal or poorly built dwellings. According to a study by the National Center for Biotechnology Information, central India had a threefold rise in widespread extreme rain events from 1950 to 2015. Long dry spells have been broken up by bursts of extreme rainfall, leaving hundreds of thousands vulnerable to the risks that come with it. In July 2019, at least 43 people were killed by heavy rains in the city. A dam that burst near the Ratnagiri district devastated seven villages, a commandant of the National Disaster Response Force said. In 2005, flooding in the state of Maharashtra killed more than 1,000 people — including 410 from Mumbai, according to a study by the United Nations Human Settlement Programme. India"s Meteorological Department recorded 940 millimeters (37 inches) of rain in the city, making it one of the worst extreme weather events the city has experienced. — CNN