The billboard collapsed on some houses and a petrol station next to a busy road in the eastern suburb of Ghatkopar following gusty winds and rain late on Monday.
Scores were trapped following the incident with rescue operations continuing till early on Tuesday. The thunderstorm brought traffic to a standstill in parts of the city and disrupted operations at its airport, one of the country's busiest.
Mumbai's municipal corporation said at least 74 people were taken to hospital with injuries following the accident and 31 have been discharged.
A rescue operation for the people remaining trapped under the billboard is ongoing. Fire services, police, disaster response officials and other authorities are all involved in the rescue efforts, the Brihanmumbai Municipal Corporation, the civic body that runs Mumbai, said on X.
News channels and posts on social media showed the towering billboard billowing in the wind for a while before it gave way and crashed to the ground.
The local weather department had predicted that moderate spells of rain, accompanied by gusty winds reaching 40-50 kilometers per hour were likely to occur in parts of Mumbai district on Monday.
There were temporary flight disruptions at the Mumbai airport, with 15 flight diversions and operations suspended for a little over an hour, ANI news agency, in which Reuters has a minority stake, reported.
Mumbai, like several Indian cities is prone to severe flooding and rain-related accidents during the monsoon season, which usually lasts from June until September every year.
