Rail incident and Sussex Police officers were pictured at the scene last night and into the early hours of this morning (Wednesday, February 3).
A Southern Rail statement, via social media, said there were reports of a trespasser in the Worthing area just after 9pm.
"As a safety precaution, the electricity that powers the line has been switched off," a spokesperson said.
"Services will be disrupted in either direction, so please allow extra time for travel."
Trains that usually run between Littlehampton and London Bridge were diverted via Horsham and rail ticket were being accepted on some bus routes across Sussex.
In an update at 9.45pm, the Southern spokesperson added: "Emergency services are dealing with an incident in the Worthing area. All lines are shut at the moment and are expected to be for some time.
"The line between Brighton, Hove, Worthing and Angmering is shut. Please avoid travel where possible, or consider making your own travel arrangements. Services will be diverted where possible."
Rail replacement bus services were not in operation.
At 11.20pm, Southern said services on the West Coastway routes remained heavily disrupted, with lines between Hove and Worthing/Angmering closed.
"Disruption is expected until the end of the day," the statement continued.
Services returned to normal shortly before 6am this morning — the incident causing nearly nine hours of rail disruption.
Have you read?: Fire breaks out at shop
1.
Emergency services respond to incident at West Worthing Station. Photo: Eddie Mitchell
2.
Emergency services respond to incident at West Worthing Station. Photo: Eddie Mitchell
3.
Emergency services respond to incident at West Worthing Station. Photo: Eddie Mitchell
4.
Emergency services respond to incident at West Worthing Station. Photo: Eddie Mitchell