National Rail has confirmed an object is caught on the overhead electric wires between Kentish Town West station and Camden Road station.
As a result, all lines are blocked.
Trains running between Gospel Oak, in Camden and Stratford, in Newham may be cancelled, delayed by up to 30 minutes or revised.
Trains will be revised to not run between Gospel Oak and Camden Road.
Disruption is expected to last until the end of the day.
