The Brihanmumbai Municipal Corporation (BMC) said the fire broke out at Hostel No. 6 at around 10:24 pm.
Two children among five injured
The injured have been identified as 12-year-old Ansh Ahirwar, 9-year-old Tahzeeb Alam, Ishwar Singh, 37, Shivkumar Singh, 34, and Anilkumar Yadav, 23.
According to a BMC official, the fire was caused by a leak in a gas cylinder pipe.
Police and BMC ward staff rushed to the spot and assisted in rescuing those trapped inside.
Injured taken to hospitals
All five injured people were initially taken to Rajawadi Hospital in Ghatkopar for treatment. Four of them were subsequently shifted to Kasturba Hospital.
Doctors said all five are stable.
A BMC official said a portion of the hostel may have been used as residential quarters, though further details about the circumstances surrounding the fire are awaited.