Exeter rail users are likely to suffer disruption to their journey this afternoon.
First Great Western say that signal problems at Exeter St David's could cause delays or services to be revised at short notice.
A signalling problem at Exeter St Davids is causing delays of up to 30 minutes to trains running through the station.
The company says the routes that will be affected are:
CrossCountry between Bristol Temple Meads and Plymouth
First Great Western between London Paddington and Penzanze and between Paignton / Barnstaple and Exmouth.