Network Rail engineers have been on-site throughout the day working to clear over 2ft of flood water from Winchburgh Tunnel in West Lothian.
More than 50mm of rain fell in just over an hour on Wednesday night, filling the tunnel with water and overwhelming its drainage systems.
Network Rail engineers, assisted by the Scottish Fire and Rescue Service, are working to clear the standing water from the tunnel and overnight inspections will take place to check the track and signalling for any damage.
Train service are expected to resume through Winchburgh Tunnel from Friday morning and customers should check their journey at National Rail Enquiries https://www.nationalrail.co.uk/ or ScotRail https://www.scotrail.co.uk/.
Liam Sumpter, Route Director for Network Rail Scotland, said: “We are working as quickly as possible to reduce the water levels so we can inspect the tracks for damage and clear out any sludge or debris that may affect the signalling systems.
“We’re sorry for the inconvenience this incident has caused our customers and will get services back on the move as soon as possible.”