Trains between London Waterloo and Clapham Junction are expected to be disrupted during the evening rush-hour until 6pm.
National Rail says all lines towards Clapham Junction are now open, following a fault on a train near Vauxhall.
But train services may still be cancelled, delayed or revised, with disruption predicted to continue until 6pm.
All suburban services from London Waterloo are not calling at Vauxhall, Clapham Junction and Earlsfield until further notice,” says National Rail.
Meanwhile passengers travelling from Waterloo or Vauxhall to Clapham Junction, are asked to use services for Reading and Windsor.
