The fire was caused by a gas cylinder explosion in the Prarthana building near the Kishore Kumar Garden in Juhu, they said.
The injured–9 men and 2 women–have been admitted to the nearby Cooper Hospital of the BMC. Eight of them are said to be critical.
The fire has been brought under control, Mumbai Police spokesperson Rashmi Karandikar told PTI.
The victims could not be identified as their bodies were charred beyond recognition, police said.