A car was engulfed in flames on Kwinana Freeway, causing traffic chaos heading northbound towards the city.

DFES crews worked to contain the fire which broke out at about 7am Wednesday.

Two crews of career firefighters from Cockburn attended and extinguished the fire by 7.12am, DFES said.

A lane of traffic at Bibra Lake was blocked, with traffic heavy back to Berrigan Drive.

Drivers were urged to drive with extreme caution and merge safely.

The fire was blamed on a mechanical fault.