All 12 had been rescued from the shop but died on the way to the hospital, officials said.
The victims were reported to be workers who were employed at the shop and were also living there.
The fire broke out around 04:00 India time (22:30 GMT) on the ground floor of the shop, trapping people in the loft, which later collapsed due to the heat.
Rescue operations are still underway, officials told BBC Marathi.
It’s not yet clear what caused the fire though poor maintenance and a lack of safety measures are often to blame. Officials said an investigation had begun.
A similar fire at a construction site in Mumbai killed six people and injured several others in September. (Courtesy BBC)