Ten fire engines and 72 firefighters and officers were called to a fire at a commercial unit in Powerscroft Road in Sidcup.
Part of the roof at ground floor level was damaged by fire.
The Brigade was called at 1235 and the fire was under control at 1538, but crews will remain at the scene throughout the afternoon damping down hotspots.
Fire crews from Sidcup, Orpington, Eltham, Lee Green and other surrounding fire stations attended the scene.
The cause of the fire is under investigation.