ARSON Squad detectives say flares were set off before fires burnt toward homes in Port Kennedy on Friday.
The fire zone had previously been used by the military and created a risk to emergency personnel, due to the possibility of un-exploded ordinance.
Strike Force Vulcan detectives are investigating the fires, one on Bayside Boulevard near Barcelona Grange and the other at the back of the Links Kennedy Bay golf course.
It is believed a person set off a flare from Port Kennedy Drive at about 10.30pm. The fire went over the golf course and landed in bushland starting the first fire.
About 20 minutes later a second flare was set off starting the second fire.
Strong winds pushed the fires toward nearby homes. About six hectares of bushland was burnt.
Detectives would like to speak to anyone who saw a flare on Friday night, or any suspicious activity in the vicinity of the fires.
Anyone with any information regarding this fire is asked to call Crime Stoppers on 1800 333 000 or make a report online at www.crimestopperswa.com.au. Callers may remain anonymous if they wish.
Rewards of up to $50,000 are available for information that leads to the identification and conviction of an arsonist.