Half of the ground floor of the five-storey building in Craven Road, Paddingtonburns, London fire brigade said Thursday at 5:30 p.m.
The brigade was called up around 4:40 pm.
Ten fire engines are on scene, including crews from Paddington, Kensington, North Kensington, Euston and surrounding fire stations.
A spokesman for the LFB said: “There are road closures and people are asked to avoid the area where possible.
“The cause of the fire is unknown at this time.”
A photo taken at the scene showed smoke filling a nearby street and rising high into the sky.
More to follow