As investigators from the Victorian arson squad dug through the remains of the home on Mantello Drive in Werribee on Sunday, police confirmed a 10-year-old and three-year-old boy, and a six-year-old and one-year-old girl had died in the fire.
Witnesses reported neighbours attempting to help the family to free the children from the home, but Molloy said the extent of the blaze meant it was beyond the capacity of bystanders to assist.
CFA commander David Clancy said the heat from the blaze meant firefighters were unable to enter the house.
One firefighter was taken by ambulance to hospital after experiencing chest pains, but Molloy said he believed the man had recovered.
Police said that the home was occupied by a family, and that the parents and another eight-year-old boy had managed to escape the fire. They were in hospital with non life-threatening injuries.
Detective senior sergeant Ashley Ryan told reporters that officers from the arson and explosives squad were conducting investigations at the scene, but did not comment on what may have caused the fire.
The three survivors from the fire are all in hospital. Police said the man had serious smoke-related injuries while the woman is being treated for smoke inhalation.
The eight-year-old boy has been taken to hospital with minor injuries.
