Police say two trains have collided in Wells and emergency services are rushing to the scene.
The incident happened near Llanbrynmair, between Shrewsbury and Mahanlath, at around 7.30pm on Monday.
It was unclear if anyone was injured.
A spokesman for British Transport Police said officers were dispatched to the route near Lambryn Mel after reports of a “collision between two low-speed trains”.
“Paramedics, fire and rescue crews and Dyfed Powys Police are at the scene and the incident is ongoing.”
A joint statement from Network Rail and Transport for Wales said the incident involved trains running from Shrewsbury to Aberystwyth at 6.31pm and from Mahanless to Shrewsbury at 7.09pm train.
National Rail said an “operational event” means line closures and trains may be canceled or modified.
Wales First Minister Eluned Morgan wrote on X: “My thoughts are with everyone involved in the incident on the Powys railway line earlier this evening.
“I would like to thank the emergency services for their response and ask to be kept informed of any developments throughout the night.”