Authorities are on the scene of a bushfire in Barragup, near the corner of Pinjarra Road and Dunkerton Road.
A spokeswoman from the Department of Fire and Emergency Services confirmed the fire started just before midday on Wednesday.
The blaze saw traffic diverted across both lanes of Pinjarra Road, with thick smoke blanketing the area.
Mandurah resident and witness at the scene James Crisp said the fire ignited when a tanker collided with low-hanging electrical wires.
"The tanker just hit the wires and once they hit the ground the whole thing just sparked up," he said.
"It was pretty crazy to see."
For more information on the fire to stay up-to-date visit emergency.wa.gov.au