A person has been hit by a train between Worthing and Littlehampton, according to Southern Rail's Twitter account.
Tweeting this afternoon, the account said it was 'with great sadness' that is must report a person being hit by a train between the two towns.
A further tweet said all lines had been blocked and replacement buses had been requested.
An estimated time of arrival for the buses was not known, said the tweet.
British Transport Police have been approached for more information.