The victims were asleep when the fire broke out. (Agencies)
The incident occurred in Kailash Apartments in Vikhroli's Siddharth Nagar around 3.15 a.m., according to an official of BMC Disaster Control.
The victims are Gautam Shalivan, 55 and his wife Poornima, 50, their son Vishal, 32 and grandson Ayush, 10.
Four people in the nearby flats were injured in the blaze. The injured were admitted to Sion Hospital.
Preliminary investigations revealed that a short-circuit could have led to the fire, which is now under control.
The victims were asleep when the fire broke out.