All lines between East Croydon and Gatwick Airport are blocked, according to a statement from Southern Rail at 5.10pm.
It said on social media, “Due to a fault with the signalling system between East Croydon and Gatwick Airport all lines are blocked.
“Services running through these stations will be cancelled or delayed.”
The rail operator added at 5.20pm that Southern tickets can be used on the following services at no extra cost:
• Metrobus routes 272, 271, 430, 460 and 100.
• TfL buses route 405.