The area near the Winchburgh Tunnel was hammered by heavy rain yesterday, leaving the track and tunnel completely unusable and prompting ScotRail to suspend all trains using that route.
All train services between Glasgow Queen Street and Edinburgh are now being terminated at Linlithgow, ScotRail warned in an update around 06:20 on Thursday.
Customers can travel on services between Glasgow Queen Street Low Level and Edinburgh via Airdrie, and Glasgow Central to Edinburgh via Shotts but lengthy delays can be anticipated.
ScotRail said replacement bus services are running from Linlithgow to Edinburgh Park are running.
Services were disrupted from 7pm onwards last with some travellers stranded on affected routes for nearly three hours.
In a statement last night ScotRail said: "Water levels outside the Winchburgh Tunnel are beginning to drop, though there is still a lot of water to be pumped away inside the tunnel. Overnight, Network Rail’s engineers will inspect the tunnel, to make sure it’s safe for trains to run tomorrow."
For the latest line updates visit ScotRail's journey checker.