What Southern Rail has described as an 'operational incident' has caused delays on the rail network between Seaford and Lewes.
According to Southern Rail's website, the incident happened on the 6.50am Seaford to London Victoria service and has led to cancellations to their Seaford services this morning.
The statement said that Southern's team was 'working hard to get services back to the booked timetable as quickly and safely as possible' but trains between Seaford and Lewes were affected.
All lines have reopened, but disruption was expected until 9am.
The statement said: "Whenever an operational incident occurs you can feel rest assured that an internal investigation will take place in order to prevent the situation re-occurring."