A safety inspection at West Wickham has led to the line being blocked, affecting the Hayes to Charing Cross line.
National Rail is advising that disruption could continue until 11:30am with trains either being delayed or cancelled.
Other trains may instead run as far as Elmers End and start from Clock House back towards London.
Which stations are affected?
Travel between London Charing Cross and Hayes is currently affected, which could impact travel on this line, including the south east London stations of Ladywell, Catford Bridge, Lower Sydenham and New Beckenham.
Alternative routes
Southeastern is advising customers that their tickets may be used to complete their journeys on London buses between Lewisham and Hayes, London Trams from Elmers End and Southern and Thameslink services from East Croydon via any reasonable route.
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