Four railway workers in Britain were killed today while working on the west coast mainline in Cumbria, police said.
They were hit by a trolley unit carrying rail lines which had come loose from a works train, according to early reports of the accident.
The men were working at Tebay Old Yard when the accident happened 6.05 am. Three more workers were injured, one seriously, and were Cumberland Infirmary, Carlisle. Three more men escaped injury.
There were 10 workers on the line when the accident happened at the Tebay Old Yard, between Kendal and Penrith.
Network Rail had taken over the track from the service operators, Virgin, so the work could be done.
Network Rail gave no further details about what happened. The dead men were working on the delayed West Coast mainline improvements, according to Virgin.
The line was being updated to accommodate the firm's new tilting "Pendolino" trains.
A Virgin spokesman said the men died after a trolley carrying the new tracks "apparently ran away".
"An engineering vehicle apparently ran away in some way and unfortunately killed engineering staff," he said. It is believed that the trolley unit was on the tracks and broke away from a main rail unit and struck the men.
Chris Connell, from British Transport Police said: "The accident involved railway workers and a trackside vehicle that they load and unload rail lines from.
"The vehicle was on the tracks at the time.
"We have got officers down there taking photographs, we will be looking at the carriage involved, we will looking to make sure that the equipment was functioning properly, that the safety records were up to date that everybody was trained properly."
Mike Head, of Cumbria Police, said they were liaising with the Health and Safety Executive and British Transport Police and an investigation had been launched.