Twelve fire engines and around 80 firefighters tackled a fire on The Broadway in Wembley.
Half of the ground floor of a shop with flats above was alight. Part of the ground floor of a neighbouring shop was also alight, along with outbuildings at the rear of the properties. Around 50 people were evacuated before the Brigade arrived.
Seventeen gas cylinders were cooled and removed as a precaution as some can explode when exposed to heat.
The Brigade's 999 Control Officers took more than 40 calls to the blaze.
The Brigade was called at 1409 and the fire was under control by 1823. Fire crews from Ealing, Wandsworth, Poplar, Mill Hill, Tooting and surrounding fire stations attended the scene.
The cause of the fire is under investigation.