Two people with serious burns were found on a vacant block and hosed down by a neighbour after a suspected drug lab explosion in Camillo overnight, police say.
Neighbours said they heard one large explosion followed by about 10 smaller blasts just after midnight.
"There was one loud bang then 10 smaller ones," one man said. "You would have heard it from miles away."
He said a man and woman emerged on fire and screaming in pain, with the man running off down the street.
"Our first concern was that their young son may have been in there as well," he said. "Thank god he wasn't."
A 14-year-old arrived at the property around 7.30am with other relatives and spoke with police before leaving.
Firefighters were called to the Excalibur Circle property just after midnight and took just over an hour to bring the blaze under control.
"At around 12.20am, police were called to attend and located two people in vacant land near the house," a police spokeswoman said this morning.
"Both had suffered extensive burns. A neighbour assisted them by hosing them down."
The man, aged 33, and 49-year-old woman were rushed to Royal Perth Hospital with serious burns.
A DFES spokesman said the cause of the explosion and fire was still under investigation.