Emergency services are at the scene after two trains crashed.
Network Rail and Transport for Wales (TfW) said the crash happened between the 18:31 BST service from Shrewsbury to Aberystwyth and the 19:09 service from Macyhnlleth to Shrewsbury, at about 19:30 on Monday.
The crash happened near Llanbrynmair, in Powys, and the line is closed while emergency services work, a joint statement from the operators said.
“Our main priority is the safety of our passengers and colleagues,” it added.