The West Coast Main Line has been blocked by a landslip between Coventry and Rugby, and up trains are being replaced by buses on this section.
Down Avanti West Coast trains towards Coventry are being disrupted, and London Northwestern trains are not running in either direction between Northampton and Coventry.
Network Rail engineers have been clearing vegetation from the railway embankment at the site of the slip, so that the scale of the damage can be assessed.
London Northwestern Railway customer experience director Jonny Wiseman said: ‘This landslip has resulted in a significant amount of earth movement next to the railway, meaning it is not safe to run trains through the area until Network Rail has completed emergency earthworks.’
Network Rail operations director Phil Barnes said: ‘“With one of the two tracks in this area closed to trains, a reduced service is running through the area and we apologise for the disruption.’
National Rail is predicting that the disruption will continue for at least the rest of the day.