Kwinana Freeway has been closed in both directions due to a bushfire burning in Wellard.
Smoke over the road has prompted the closure between Mundijong Road and Mortimer Road.
The fire has been burning in nearby bushland since about 11am, with emergency crews at the scene.
Motorists are asked to avoid the area, reduce speed and drive carefully due to smoke.
Further information will be released by Main Roads WA as the situation changes.
Up to 30 firefighters are battling the blaze, with air support assisting ground crews.