A fire at a recycling yard in the Perth suburb of Bayswater is causing significant traffic delays for motorists on the Tonkin Highway.
Firefighters say a huge pile of mulch caught fire at Pure Earth just after 3:00 am and is expected to burn for up to 12 hours.
It is blowing smoke across the busy highway and more than 50 firefighters are at the scene.
The Department of Fire and emergency services spokeswoman Kathy Nastov says motorists should avoid the area.
"It will be down to one lane from Morley Drive to Guildford Road, heading south and we will also have a road closure on Collier Road from Tonkin Road East to Jackson and Gray Street," she said.
"It is causing quite a bit of smoke issues."
Ms Nastov says the smoke will be monitored.
"At the moment we're waiting for the attendance of the DEC [Department of Environment and Conservation] pollution response vehicle.
"They will do some smoke monitoring and ensure there's no harmful chemicals in the smoke and ensure that it is safe for residents and neighbouring industrial areas."