Rail users are being told to expect delays of up to an hour following a fatality at Wimbledon station.
Wimbledon station was closed after a man was struck by the 13.35pm South West Train Service from Waterloo to Weymouth.
A British Transport Police spokeswoman said: "BTP officers were called to the line close to Wimbledon station on Saturday afternoon after a report that a person had been struck by a train.
"Officers from British Transport Police and the Metropolitan Police attended the incident. Medics from the London Ambulance Service also attended, but the person was pronounced dead at the scene.
"The death is not being treated as supicious."
The London Ambulance Service confirmed the person killed was male, but had no further details.
A South West Trains spokeswoman said Wimbledon station re-opened at about 3.10pm, but that delays of up to an hour in both directions could be expected for a few hours yet.
First Capital Connect services through Wimbledon are unaffected.
Train tickets are being accepted on buses.
Weekend engineering works are also taking place across parts of the South West Trains network.
Tickets are being accepted on Southern services between Clapham Junction and Battersea Park. Buses replace trains on Sunday.
Journey times will be extended by up to half an hour.