Two railway workers who died after being struck by a train near Port Talbot could not hear it approaching due to their ear defenders, British Transport Police have said.
The men, aged 58 and 64, were both pronounced dead at the scene, while a third Network Rail worker was treated by medics for shock.
An investigation is now underway into what caused the fatal crash, but it is understood signalers were unaware workers were on the line Swansea and London Paddington.
One railway worker said: The driver immediately called in the accident saying he had struck the three workers and ambulances were called.
A signal worker didnt know that they were there. It could be that they hadnt notified the right people.
There have been a lot of near misses on the tracks recently with contractors working on the line.
The Great Western Railway passenger service from Swansea to Cardiff was brought to a halt just outside Port Talbot Parkway at around 9.29am on July 3.
Union bosses called the incident an appalling tragedy and have demanded answers from Network Rail.
Passengers were kept on the train for more than two hours before being evacuated onto buses.
One shocked passenger described seeing a large number of emergency service vehicles at the scene, while another said the impact of the incident was not felt on-board.