KWINANA Freeway has been closed in both directions as firefighters battle a bushfire which they believe was deliberately lit.
Nearly 100 volunteer and career firefighters are battling the blaze, which broke out just after 1.15pm yesterday.
Three helitacs were dispatched to the scene as well as around 18 fire appliances to bring the fire under control.
The fire started near Bertram Primary School but is now heading along Johnson Road towards Thomas Road has has burnt about 5ha.
Smoke is causing major problems for traffic.
There is no threat to lives or homes but there is a lot of smoke in the area.
If you have a respiratory condition and you have been affected by smoke you should contact your local doctor or call Health Direct on 1800 022 222.
Main Roads closed the freeway to traffic just before 4pm.
A bushfire advice warning has been issued for people in an area east of the rail line in Bertram and west of Bombay Boulevard in Casuarina, extending north to Anketell Road in Anketell in the Town of Kwinana.
Residents have been told to stay alert and monitor their surroundings.
Firefighters battle Lake Muir blaze
Firefighters are battling a second blaze 10km south-east of Lake Muir in the Shire of Manjimup, in the South West.
A bushfire advice has been issued for people 10km south-east of Lake Muir and 10km south of Muir Highway for a fire burning in Lake Muir National Park.
There is no threat to lives or homes. Although there is no immediate danger you need to be aware and keep up to date.
The bushfire is moving at a moderate speed and has burnt through about 3ha.
DEC ground crews are being assisted by two fixed wing water bombers.
The fire is suspected to have been caused by lightning
Yesterday's fires come just days after a blaze, caused by a falling power pole, ripped through the outskirts of Chidlow on Thursday.
While no homes were destroyed during the incident, flames from the ferocious fire came close. A number of sheds and fences were destroyed and farmland was burnt.
Read more on Perth Now.