Plumes of thick black smoke has led to the closure of the M1 near Brent Cross causing major disruption to motorists.
Around 80 firefighters and officers are tackling the huge raging inferno at a builders' merchant on Brent Park Road.
Video footage from Hitoshi Yoshioka shows thick blacn smoke billowing across the M1.
Drivers were warned a number of road closures were in place including a stretch of the M1 in both directions from J1 to J4.
The M1 northbound has since reopened but the southbound carriageway remains closed.
People using East Midlands and Thameslink train services are also being affected with the train line closed between Hendon and Cricklewood.
A large area of a wood working shop measuring around 100 metres by 20 metres is up in flames.
The extent of the blaze has also seen two aerial appliances in use at the scene to help tackle the fire from above.
London Fire Brigade , station manager Claiton Murray who is at the scene said: "This is a large, challenging fire and crews are working extremely hard to bring it under control as quickly as possible.
"Around half of the workshop is alight.
"The fire is producing a considerable amount of smoke so we are advising people living and working in the area to keep their windows and doors closed as a precaution."
Motorists are advised to avoid the area and commuters should check travel updates and can use their tickets on other train, tram and bus services.
The Brigade's 999 control officers have taken more than 20 calls to the fire.
LFB were called at 3.45pm to reports of a fire and sent crews from Hendon, Stanmore, West Hampstead and surrounding fire stations to the scene.
The cause of the fire is currently unknown.
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