Many of the victims were young women who were attending a birthday party on the rooftop when the fire broke out. Doctors said they died of asphyxiation, apparently as they tried to flee the burning building.
Local media reported that a false ceiling had collapsed in the four-storey building in the Indian financial capital, trapping people inside as they tried to escape.
The fire was extinguished in the early hours but an AFP reporter at the scene said the rooftop where the party was taking place had been gutted, with charred ice buckets and ashtrays strewn around.
“Fourteen people have succumbed to their injuries and remaining victims have been discharged from the KEM hospital. Most of the deaths were due to asphyxiation,” Avinash Supe, dean of local KEM hospital told AFP.
Police said they were investigating the cause of the fire, and had filed a preliminary case against the restaurant’s owners.
Eleven of the victims were female partygoers, according to authorities.
One woman who said she was in the building at the time told of the desperate scenes as people tried to escape.
“There was a stampede and someone pushed me,” Sulbha Arora said on Twitter.
“People were running over me even as the ceiling above me was collapsing in flames. Still don’t know how I got out alive. Some powers were definitely protecting me.”
Accidental fires are common across India because of poor safety standards and lax enforcement of existing regulations.
A fire swept through a sweet shop in Mumbai earlier this month, sparking a building collapse which killed 12 sleeping workers.
In September, a gas cylinder exploded in an unfinished building in Mumbai killing six people.
Such disasters are particularly common in Mumbai, where millions live in cramped, dilapidated properties because of high rental prices. Activists say builders and landlords often cut corners on safety to save costs.
Television footage of the latest disaster showed fire engines and emergency teams rushing to the scene as the building was being consumed by flames and dark plumes of smoke rose into the night sky.
Firefighter Sanjay Hiwarle told reporters the blaze was brought under control during the night and a “cooling operation” was under way.
The restaurant was in the city’s Kamala Mills compound, which also houses hotels and offices.
Several media organisations also use the building and at least three national news channels were affected by the fire, including Times network’s Times Now, Mirror Now and ET Now channels.
India’s Prime Minister Narendra Modi tweeted that he was “anguished by the fire in Mumbai”.
“My thoughts are with the bereaved families in this hour of grief. I pray that those injured recover quickly,” he said.