Teen dead after shed fire near Perth

A teenager has died in an overnight house fire south of Perth.

Ashley Graham, 16, was inside a shed that had been converted into living quarter when the blaze broke out around 3am.

Four fire crews worked to extinguish the fire.

Arson squad investigators are at the Forrestdale home to determine the cause of the fire. It is not believed to be suspicious.

Relatives told 9NEWS they believe the fire may have been sparked by a mobile phone battery.

Ashley's sister said her brother was down to earth and hard-working. He was a top student who was awarded Dux at his school in Byford.

A report is being prepared for the coroner.