FESA Fire Investigation and Analysis Branch investigators and Police Arson investigators have completed their site investigations at 12 Hancock St Mandurah.
The fire resulted on the death of a 57-year-old woman early Thursday morning.
The fire started in the front bedroom of the brick and tile home about 4.30am
The woman was located by firefighters in the lounge room.
The are no suspicious indicators and the cause is undetermined.
No smoke detectors were installed.
A man was taken to hospital with smoke inhalation and burns to his chest after he attempted to save the woman.
No other people were in the house at the time of the fire.