A busy section of the North Circular was shut during rush hour after a car burst into flames in the road.
Emergency services were called to the A406 westbound carriageway just before the Crooked Billet roundabout at about 7am after the fire broke out.
A Met spokeswoman said there were no injuries as a result.
Part of the road remains shut while police and fire crews investigate. Dramatic pictures from the scene show the car had been moved to chevrons in the middle of the road.
Drivers have been warned to expect severe delays because of the closure with traffic also moving slowly on the eastbound carriageway.
TfL Traffic News tweeted: "A406 Crooked Billet Underpass, Westbound, The road is closed.Car fire. Plse (sic) use other routes and expect long delays."
A Transport for London spokesman said the cause of the blaze is unclear at this stage.
