Emergency services attended an incident on the railway line between Brighton and Worthing after a person was struck by a train.
The incident has resulted in the suspension of all rail services through the affected section.
Network Rail and train operators have confirmed that no services are currently operating through the area and this situation is expected to continue for several hours.
Passengers travelling through the region have been advised to seek alternative transportation options as no trains will run along the affected route until operations can resume safely.
Train operator Southern Rail has indicated that significant disruption is anticipated throughout the afternoon, with services not expected to normalise until 17:00.
A representative from the rail company expressed regret over the inconvenience caused to passengers and acknowledged the impact the incident would have on individual travel plans.
Emergency responders were observed at Southwick station as part of their attendance at the scene.
The following stations on the affected line have no train service in either direction: Hove, Aldrington, Portslade, Fishersgate, Southwick, Shoreham, Lancing and East Worthing.
No alternative rail services are operating to or from these locations until the incident has been fully resolved and the line declared safe for passenger operations.