Eight fire engines and around 60 firefighters tackled a fire at a builders yard on Teignmouth Close in Edgware.
A single-storey outbuilding in the yard between Teignmouth Close and Dale Avenue was destroyed fire. A van and further contents in the yard were also destroyed. A 25-metre cordon was in place as a precaution. There were no reports of any injuries.
Station Commander Andy McKay, who was at the scene, said: "The fire was producing a substantial amount of smoke.
"We appreciate it was a very hot night, but we urged local residents to keep their windows and doors closed until the smoke subsided. We also asked people to avoid the area whilst we worked to make the scene safe."
The Brigade's 999 Control Officers took almost 30 calls to the blaze.
The Brigade was called at 2013 and the fire was under control by 0005. Fire crews from Stanmore, Mill Hill, Hendon, Finchley and surrounding fire stations attended the scene.
The cause of the fire is under investigation.