Fifteen fire engines and around 100 firefighters were called to a fire near Elephant and Castle Railway Station on Monday.
Six people were treated by the London Ambulance Service at the scene and one person was taken to hospital.
Three commercial units underneath the railway arches were completely destroyed and around 600 people were evacuated from surrounding properties as a precaution.
All trains were stopped from coming into the overground station and road closures were put in place.
Station Commander James Ryan, who was at the scene, said: 'There were significant road closures in place and people were asked to avoid the area. Local people were advised to keep their windows and doors closed whilst firefighters worked to bring the fire under control. The station and nearby buildings were evacuated.'
The Brigade was called at 13.43 and the fire was under control by 17.58. Fire crews from Old Kent Road, Lambeth, Soho, Whitechapel and surrounding fire stations attended the scene.
The Brigade's Fire Investigation Team is continuing work to establish the cause of the fire.