A number of South West Trains services between Surbiton and Woking were cancelled or delayed after a woman was hit and killed by a train at Esher station.
The operator confirmed delays into and out of London Waterloo would last into the afternoon.
A British Transport Police spokesman said: "Officers from BTP and Surrey Police attended along with colleagues from the South East Coast Ambulance Service and a woman was pronounced dead at the scene.
"Officers are now working to identify the woman and inform her family.
"The circumstances of her death are not being treated as suspicious and a file will be prepared for the coroner."
Magazine editor John Honeywell, 67, was on the train. He told this website: "As the train was passing through Esher station at high speed, the driver sounded the horn and applied the brakes for an emergency stop.
"I am in the front carriage of the 12-car train and I am currently level with the far end of the car park.
"No trains have run into London since the incident occurred.
"There were a number of people on the platform who will have witnessed what happened.
"I believe we may soon be moving to Surbiton where we will leave the train."
A Surrey Fire and Rescue spokesman said firefighters from Esher and Painshill had been called at 10.20am.
- Do you know more? Call the newsdesk on 020 8722 6313 or email rachel.dickerson@london.newsquest.co.uk
South West Trains said: "The emergency services were called to an incident between Surbiton and Woking, where a person has been struck by a train earlier this morning.
"All lines have now reopened and trains are on the move in both directions.
"South West Trains tickets will be accepted by London Underground on any reasonable route. Passengers travelling towards London from Basingstoke may also use their tickets to go via Reading on GWR, and then to Paddington from there."
TRAVELLING BY TRAIN: WHAT YOU NEED TO KNOW
- All Waterloo to Woking stopping services starting from 11:20, will be cancelled in both directions
- All London Waterloo to Exeter St. Davids services will start and terminate at Basingstoke in both directions
- London Waterloo to Basingstoke services will run as booked; some may terminate and restart at Woking or be diverted to run via Chertsey
- London Waterloo to Portsmouth services will run as booked on the way out, and on their return, will run via Cobham
- London Waterloo to Weymouth services will run via either Chertsey or Guildford, or terminate and restart at Woking
- London Waterloo to Portsmouth via Eastleigh services will all start and terminate from Basingstoke
- London Waterloo to Alton services will stop additionally at most stations between Surbiton and Woking
- Alton to London Waterloo services will run either via Guildford or Cobham and Stoke D'Abernon or terminate and restart at Woking
If you are experiencing problems with your mental health, visit your GP
Samaritans lends a confidential ear to those in distress; call 116 123
Mind promotes the views and needs of people with mental health problems; call 03001 233 393
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here