London Fire Brigade is battling a fire at East Duck Lees Lane in Enfield that has caused acrid black smoke to billow miles across the capital.
Ten fire engines and 72 firefighters and officers are at the scene tackling the blaze, which has engulfed hundreds of wooden pallets.
The whole of the yard and 25 motor vehicles have been damaged by the blaze and firefighters are now cooling potentially explosive gas cylinders.
Residents near the fire have been advised to close their windows and doors to prevent smoke entering homes and neighbours are being evacuated from the area.
A London Fire Brigade spokesperson said: "Firefighters are at the scene tackling the industrial unit blaze. There is a lot of thick black smoke in the local area so we'd ask local residents to close their doors and windows.
"The Brigade was called at 10:10am on Tuesday 21 July. Fire crews from Enfield and surrounding stations are at the scene.
"A number of gas cylinders are involved in the fire. Fire crews will be cooling them down as some cylinders can explode when exposed to heat. The cause of the fire is not known at this stage."