Elderly woman dies in Sydney house fire

A woman in her 90s has died after being overcome by smoke in her burning home, despite the heroic efforts of three passers-by.

Authorities are investigating a suspicious fire which engulfed a shop in Adelaide. (AAP)

Three brave members of the public tried in vain to force their way into a burning house to save an elderly Sydney woman.

Firefighters were called to the Punchbowl home about 6.30am on Sunday where they found three passers-by trying to fight the blaze with a garden hose and get to the woman in her 90s.

The firefighters rescued the unconscious woman, who was taken by ambulance to hospital, where she died a short time later.

The fire is not believed to be suspicious.