Windy weather caused an advertising board to come crashing down.
Fire crews were called to clean up the mess in Old York Road, Wandsworth, at 8.30pm last night.
It is thought stormy weather resulted in the board to come lose, which was under the railway bridge.
Firefighters were told someone was trapped underneath, but discovered this was not the case on arriving at the scene.
It was cleared within 20 minutes, with buses temporarily on diversion.