Twelve fire engines and around 80 firefighters were called to a fire at a range of single storey industrial units on Water Road in Wembley.
The whole of two units were destroyed and a third also sustained fire damage.
Station Manager Dan Johnson, who was at the scene said:
"We have asked local residents to keep their doors and windows closed as there was still a lot of smoke in the nearby area."
The Brigade was called at 1714 and the fire was under control at 0022. Fire crews from Park Royal, Wembley and surrounding fire stations attended the scene.
The cause of the fire is under investigation.