Network RailNetwork Rail has said a suspected landslip has closed the Oban branch of the West Highland Line.
Engineers have been sent to the site near Falls of Cruachan in Argyll to investigate.
ScotRail said the line was shut between Dalmally and Falls of Cruachan due to suspected flooding and has warned of disruption to services.
It said services between Glasgow Queen Street and Oban could be cancelled, delayed or revised.
ScotRail also said services between Glasgow Queen Street and Mallaig were subject to delay or revision.
Argyll’s A85 is also closed at Bridge of Awe, Lochawe, due to a risk of falling rocks.
Traffic Scotland said an 84-mile diversion had been put in place.
