Trains between Shrewsbury and Birmingham New Street were affected by issues with signals between Shrewsbury and Oakengates this morning.
Disruption is expected to continue until about 4pm, and replacement buses are travelling in both directions between Shrewsbury and Wolverhampton.
A spokesman for National Rail said: "The fault with the signalling system between Shrewsbury and Oakengates has been resolved, allowing lines to reopen.
"However, whilst services recover, journeys between Shrewsbury and Wolverhampton may continue to be cancelled or delayed by up to 30 minutes."
The first West Midlands Railway service to run from Shrewsbury will be the 12.13 Shrewsbury to Birmingham New Street.
Local democracy reporter Andrew Morris said he had already been sat on the train when it was cancelled.
"A great start to Monday," he tweeted. "I was sat on the train to Shrewsbury from Wolverhampton. Actually sat on it. Then it was cancelled. And all trains are. Because of a signal fault.
"nobody has a clue what’s going on and 'there might be some buses later today'.
"Public transport fails yet again. Good luck to those still waiting."
Network Rail said signal failure can be the result of a number of different issues, including a power cut or blown fuse.
It says its main priority when signals fair is to keep passengers and staff safe, while keeping delays to a minimum.