Urgent repairs to the tracks took place between Eastbourne and Polegate earlier today, which resulted in all lines becoming blocked, National Rail said.
Trains were not able to run between the stations for some time and a replacement bus service was in operation.
A spokesman for Network Rail said this morning: “Earlier this morning the 07:37 Polegate to Eastbourne service developed a fault prior to departing.
“The driver was unable to draw power from the third rail and subsequently blocked the line for around 20 minutes.
“The driver contacted train technicians and was guided through a repair process, where they were able to get power back to the train and move this to one of the depots where further inspection will take place.
“Unfortunately Network Rail engineers have assessed the line and reported that there is damage to part of the track, therefore for safety reason, until this has been repaired and made safe for trains to pass over again, services have had to be suspended.”
Southern tickets were being accepted on Brighton and Hove Buses.
UPDATE: Southern said disruption following the urgent repairs to the track between Eastbourne and Polegate has now ended.
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