Southern Rail reported, just before 9pm, that the incident happened between Horsham and Arundel, with ‘all lines blocked’.
“Services running through these stations have been suspended,” a Southern statement read.
"We expect substantial disruption in this area for the rest of the night.
“We are currently arranging alternative transport but this will take some time. Please consider avoiding travel, or travelling once we can confirm alternatives are in place.”
Southern said trains are being held in stations ‘where possible’, adding: “If you are on a train in the area currently at a stand in between stations, please listen to all announcements if you are able to.
“If you require any assistance, please speak to onboard staff.”