The 13-year-old boy's mother was across the road at a shopping centre when the fire broke out at the home on Greenwood Street, Newcomb on Tuesday afternoon. She arrived home to find her home ablaze, Channel Seven reported.

The teenager did not survive the fire, which reportedly started at the back of the house. Police said they later found his body inside after the fire was extinguished.

The boy's grandmother and two brothers, aged nine and 10, escaped unhurt.

Five fire trucks arrived at the house about 2pm to find half of the building engulfed in flames.

The Country Fire Authority had the blaze under control within about half an hour.

Police investigators were working at the scene, but do not yet know how the fire started.