Five others, who sustained injuries, were hospitalised and their condition is stable.
According to the police, the fire broke out at the apartment in Vadapalani around 4.45 a.m. and several two wheelers that were parked on the ground floor caught fire.
Thick black fumes bellowed upwards suffocating to death four persons -Selvi (30), Meenakshi (60), Shalini (10) and Sanjay (4).
Police are investigating the case. Forensic experts have inspected the accident site.