Investigators believe a toy fell onto a bar heater in a Geelong home and caused the fire that led to the deaths of two young girls and put their baby sister in hospital.

The girls' father, Hashem Qorbani, frantically pulled his young daughters, Sana, 3, and Saba, 2, from their smoke-filled bedroom after the fire broke out early on Thursday morning.

He made a mad dash with his daughters to a doctor who lives nearby, before driving them to hospital with their mother, but the girls could not be revived.

The couple's six-month-old daughter, who was sleeping in a separate room, is in hospital being treated for smoke inhalation. Her condition is not life threatening.