Bricks tumbled onto the tracks at the Bakerloo line's London Road Depot on Tuesday night when a car crashed into a wall above the open-air sidings.
The British Transport Police says no-one was injured.
Transport for London's emergency response unit spent several hours clearing masonry and fencing from the tracks.
There were severe delays to northbound Bakerloo line services during the morning rush hour on Wednesday as a result of the incident.
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