Witnesses described how people were thrown to the floor of the train and pictures of the scene showed part of one of the carriages crumpled in the impact.
Investigators were at the scene near the village of Llanbrynmair in Powys on Tuesday morning to try to establish why the trains had collided on the line, a single-track section.
The incident took place close to a passing loop on the largely single-track Cambrian line, where one train should stop and the other proceeds at low speed on a small loop of track. It appears that the train that should have stopped was unable to do so, but the collision was slow enough that neither train derailed, The Guardian reported.
A multi-agency investigation is under way. Leaves on the line will be one possible avenue of investigation. Network Rail spends millions clearing autumn leaves from lines because they are the equivalent of black ice on roads.
It is believed that some passengers suffered broken bones, although police said their injuries were not believed to be life-threatening or life-changing.
Jonah Evans, 25, a witness to the collision, said: “There was a train that was stopped and the other train couldn’t stop. And the driver couldn’t get out the way with a train in front. The driver ran in and sat on a chair and said brace yourselves – we’re about to hit a train. Someone lost their teeth, cracked ribs. Because the driver told us it was happening, we could kind of get ready.”
Anthony Hurford, who had been travelling to Shrewsbury, told BBC Breakfast: “The word that keeps coming to my head is just brutal really. Just going from, I don’t know how fast we were going, maybe 40, 50, 60 miles an hour, to nothing in the blink of an eye, the report added.
MA/PR