Investigators examining a fatal crash involving two trains in mid Wales have found evidence suggesting one of the trains may have slid while braking.
The Rail Accident Investigation Branch (RAIB) said the condition of the track on the approach to the collision point meant “adhesion” between wheels and rails was “relatively low”.
Initial evidence suggests the collision near Talerddig in Powys at 7.26pm on Monday night occurred at a speed of approximately 15mph.
A man in his 60s died, four other people were seriously injured and 11 more sustained injuries requiring hospital treatment.
The dead man’s next of kin have been informed.
The trains were both Class 158s operated by Transport for Wales (TfW).
It is believed the 6.31pm service from Shrewsbury to Aberystwyth travelled beyond where it should have stopped and hit the stationary 7.09pm service from Machynlleth to Shrewsbury.
The RAIB said: “RAIB’s initial inspection of the track on approach to the point of collision found evidence that wheel/rail adhesion was relatively low, suggesting that the train may have entered into wheel slide when braking.
“This will be an area of ongoing investigation.
“Our investigation is in its very early stages and an additional update will be available in the coming days once RAIB has gathered and analysed further evidence.”
Network Rail said one of its railhead treatment trains – which tackle autumn leaf fall – ran along the line where the crash happened on Sunday night.