Emergency services are responding to a crash on the Forrest Highway in West Coolup.
The crash happened around 7.45am on Saturday between Heron Point Road and Old Bunbury Road.
It is understood a car and a bus collided.
It is not yet known if anyone was injured.
Motorists travelling on Forrest Highway in the West Coolup and Birchmont areas have been advised to drive with caution as there is reports of thick smoke.
The Forrest Highway has since reopened.