Sheep on the line disrupted railway services between Brighton and Seaford earlier although they have now been herded to safety.
But passengers have been warned to expect delays of up to 20 minutes until 7.45pm.
Southern said: “The earlier animals on the railway in the Southease area have now been removed from the line, allowing trains to begin running at line speed again.
“Until service recovers, trains running between Seaford and Lewes may still be delayed by up to 20 minutes. Disruption is expected until .45pm.”
The train operator said: “Trains have been delayed due to a number of sheep that entered the railway in the Southease area.
“Due to safety concerns, trains ran at reduced speeds past the sheep until Network Rail teams were able to access the site and remove the sheep from the track.
“You may be entitled to compensation if you experience a delay in completing your journey today. Please keep your train ticket and make a note of your journey, as both will be required to support any claim.”
