Transport for Wales (TfW) has had to cancel many services after the broken rail was found between Leominster and Ludlow.
The train operator has put on replacement bus services along the route.
Passengers have also been advised to find alternative routes, with TfW saying ticket acceptance is in place with operators Cross Country and GWR.
A Transport for Wales spokesperson said: “Services between Ludlow and Shrewsbury are currently disrupted due to a broken rail.
"Our industry partners Network Rail are working hard to resolve the issue, but services are expected to be disrupted for the rest of the day. Replacement bus services are in operation, and tickets will be accepted on Avanti West Coast, West Midlands Railway, CrossCountry and Great Western Railway services for alternative routes.”