Train services between Wolverhampton and Birmingham New Street have been suspended while emergency services deal with an incident near Sandwell and Dudley railway station.
All lines on the busy route have been closed to allow emergency crews to carry out their work safely, with passengers being warned to expect disruption into the early afternoon.
The closure is affecting a number of operators running services through the Black Country and between Wolverhampton and Birmingham.
A spokesperson for National Rail said: “The emergency services are dealing with an incident between Wolverhampton and Birmingham New Street.
“To allow them to complete their work safely all lines are closed.”
The incident is understood to be in the area around Sandwell and Dudley station, which sits on the main railway line between Wolverhampton and Birmingham New Street.
National Rail has advised passengers using Avanti West Coast, London Northwestern Railway, CrossCountry, Transport for Wales and West Midlands Railway services between Wolverhampton and Birmingham that their journeys could be affected.
Trains may be delayed, revised, cancelled or diverted while the emergency services remain at the scene and the railway is closed.
Disruption is currently expected to continue until early this afternoon, although passengers planning to travel through the area are advised to check their journeys before setting off.
A spokesperson for West Midlands Railway said: "Emergency services are dealing with an incident at Sandwell and Dudley."
"Services in the area are currently suspended. Further updates will follow as soon as we have more information."
People whose journeys are affected have also been given additional flexibility over when they can travel.
Passengers can use their tickets on another service operated by a participating train company either up to two hours before or up to two hours after their original scheduled departure time.
West Midlands Railway said ticket acceptance is in place with NX buses and West Midlands Metro.
The railway between Wolverhampton and Birmingham is a major route through the West Midlands, serving stations including Dudley Port and Sandwell & Dudley before trains reach Birmingham New Street.
Passengers intending to travel through the affected area should allow additional time for their journeys and check the latest information from their train operator.
No further details about the nature of the incident have been provided at this stage.
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