Train services to and from Gatwick were delayed well into Tuesday evening after urgent repairs were carried out on the track earlier in the day.
Travellers were initially warned that train services running through Three Bridges and Gatwick may be delayed by up to 30 minutes or revised and that disruption was expected until 16.30 on Tuesday.
"Services are still able to run through these stations, however it is likely that alterations will be made," said National Rail.
" Due to fewer platforms being in service, some platform changes may occur so please listen for station announcements and look at information boards."
Network Rail later said lines had reopened but services running through Gatwick and Three Bridges may still be delayed or revised.
It said disruption is expected until 9pm.
