Major disruption has caused delayed trains at London's Euston station.
National Rail said disruption was expected to last until 21:30 GMT on Thursday after an incident on the track between the station and Rugby, Warwickshire.
It said emergency services had been dealing with the incident, and lines had now reopened.
However, passengers have been told trains may still be cancelled, delayed by up to 60 minutes or revised.
National Rail said the Avanti West Coast route between Edinburgh, Glasgow Central, Blackpool North, Liverpool Lime Street, Holyhead and London Euston was affected.
The London Northwestern Railway between Crewe, Birmingham New Street and London Euston is also facing disruptions.