Company spokesperson Joe Cerenzia told International Longwall News it was not clear yet as to exactly what had happened to motorman Gary Hoffman, 55, an employee of the operation since 2000.

“He was found either along or across the track by another motorman who was following the [man] trip. Mine employees and then outside EMTs attempted to revive but were unsuccessful," he said, adding that interviews are currently being conducted to determine the events that led up to the fatality.

The West Virginia Office of Miners' Health, Safety and Training told the Associated Press Thursday afternoon that Hoffman appeared to have lost control of a locomotive he was driving and either fell or jumped from the unit.

“[He] probably jumped off – that's what we've been told," spokesperson Jama Jarrett told the news service.

“We don't know if he jumped off and hit something or jumped off and got run over."

A request for comment and detail from the US Mine Safety and Health Administration was not returned by press time, but agency spokesperson Matthew Faraci told the AP that federal investigators are evaluating whether the locomotive may have derailed on a grade, and confirmed that the worker was operating the lead locomotive in a unit that included an engine at either end of two cars.

Investigations by state, federal and union officials have commenced.

Another Consol spokesperson, Tom Hoffman, added in an interview with the AP that Hoffman's injuries were consistent with an equipment accident.

“He was found by another motorman lying, I believe, across the tracks. We don't know much more," he said.

The fatality is the third in the US in less than a week. Last Friday afternoon, general inside labourer Adam Lanham, 18, was working at International Coal Group's Wolf Run Mining Sentinel mine in West Virginia when he was struck by a Fairchild 35C-WH battery-operated scoop.

Tuesday morning, roof bolter operator Justin Wilkin, 25, was working at Gibson County Coal's Gibson operation in Indiana when a section of unsupported roof fell on top of him.

Lanham had just five weeks of experience, Wilkin just over two years.

Historically one of the state's top producers as well as one of the safest, Cerenzia noted that Robinson Run had earned Consol's award for best safety record last year, and has won several state and federal safety awards.

The mine, with a staff of approximately 500, produces about 7 million tons per annum.