Police are investigating the cause of a bushfire in Secret Harbour.
The blaze started just after 1.30pm on Sunday in scrub near the intersection of Berryessa Parkway and Summerville Avenue.
Around 40 firefighters spent hours controlling the blaze, which caused the closure of Warnbro Sound Avenue.
A bushfire advice remains for the area.
The cause of the fire is not yet known, but anyone who saw any suspicious activity should contact Crime Stoppers on 1800 333 000.
Four hectares of land has been destroyed.

Southern suburbs electrician claims $1.8 million Lotto win
Works continue on Pinjarra's Munday Avenue extension
Halls Head support worker charged with historic child sex offences
Severe thunderstorm warning cancelled for Mandurah, Bunbury
Fortnightly red bin collections to remain in the City of Rockingham after council rejects motion
Rate rises on the way for Rockingham, Mandurah ratepayers
Harvey Police call on witnesses to serious crash
Men allegedly under the influence of alcohol when boat crashed under Mandurah Estuary Bridge
Works underway on 26 new social homes in Kwinana