Authorities say a bushfire that posed a possible threat to lives and homes in East Rockingham and Kwinana was deliberately lit.
The fire started near the intersection of Patterson Road and Charles Street around 3.18pm on Monday.
It reached a watch and act alert with nearby residents urged to leave their homes or get ready to actively defend them.
Firefighters managed to bring the blaze under control within a couple of hours.
It had burnt through 2.5 hectares of bushland.
Anyone who saw any suspicious activity at the time of the fire should contact Crime Stoppers on 1800 333 000.

A bushfire advice remains for the area. PIC: DFES
                            
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