The billboard, bigger than an Olympic-sized swimming pool, crushed a fuel station, homes and cars during a thunderstorm on Monday, trapping more than a 100 people, according to authorities.
Rescuers worked through the night to pull people from the debris on the side of a busy arterial road in the Mumbai suburb of Ghatkopar.
Some 75 wounded were rescued and 14 bodies found, said the city's civic body Brihanmumbai Municipal Corporation.
"The operation was very challenging due to the weight of the structure and the presence of flammable liquid and gas at the site," Mohsen Shahedi, a senior National Disaster Response Force officer, told Reuters.
Shahedi said the rescue operation was nearly over except for one last sweeping search.
"We believe there is no one else stuck under the debris," he said.
Videos showed the towering billboard billowing in the wind before collapsing as a dust storm and rain lashed the city, bringing traffic to a standstill and disrupting flights at Mumbai airport
The agency that owns the billboard did not have a permit from the BMC, the municipal body said in a statement. The hoarding measured about 1338sq m, it said, nine times larger than the maximum permitted size.
The BMC said it had instructed the agency to remove all its hoardings immediately.
"To prevent such accidents from happening again, instructions have been given to conduct a structural audit of all hoardings in Mumbai and immediately take down dangerous ones," Eknath Shinde, the chief minister of Maharashtra state of which Mumbai is the capital, said in a post on X.
"Out of 1,300 such hoardings in Mumbai, around 30 have not submitted a structural stability report that is mandatory every two years," said Bhushan Gagrani, who heads the BMC. "We are looking into that."
