Trains are being delayed and cancelled due to a points failure between Shrewsbury and Wolverhampton.
National Rail said the fault meant lines would be blocked, with disruption expected to last until the end of Thursday, affecting West Midlands Railway and Transport for Wales services.
Trains are unable to run between Shrewsbury and Birmingham International as a result of the failure, and an hourly rail replacement shuttle has been organised to run between Shrewsbury, Wellington, Telford Central and Wolverhampton.
On other parts of the network, passengers were advised of delays of up to 30 minutes, as well as some revisions to services.