Rail services through Gatwick Airport are being disrupted after a train hit an obstruction on the tracks.
Rail operators Thameslink and Southern first reported the issue at about 06:00 GMT on Tuesday, saying that an obstruction had been struck by a train near Salfords station, in Surrey.
The train companies say trains running to, from or through Gatwick Airport may be cancelled, delayed by up to 40 minutes or revised and services that are running may use alternative platforms at some stations.
Thameslink said its services between Three Bridges and Bedford had been suspended, and no trains would call at Salfords or Earlswood stations in the northbound direction until further notice.