Massey’s defence that a methane build up at the mine caused the explosion was discredited and a culture of shortcutting on safety at the mine was put under scrutiny in the first independent report of the incident by investigator Davitt McAteer.

“A company that was a towering presence in the Appalachian coalfields operated its mines in a profoundly reckless manner and 29 coal miners paid with their lives for the corporate risk taking,” McAteer wrote in his report.

"[Massey Energy] broke faith with its workers by frequently and knowingly violating the laws and blatantly disregarding safety practices while creating a public perception that its operations exceeded industry safety standards."

A small fireball caused by a spark between equipment and a rock face developed into "an enormously powerful blast" that rocketed through more than two and a half miles of the mine, nearly 1000 feet underground because of Massey’s lax safety measures, according to the report.

The investigation found that in the 26 days before the disaster, the company carried out rock dusting at UBB only 11.6% of the time it was requested and out of a total of 561 dustings requested, only 65 were recorded.

"Extensive tests conducted by MSHA [Mine Safety and Health Administration] after the disaster support miners' testimony that the Upper Big Branch mine was poorly dusted," the report stated.

"A well dusted mine would have put the brakes on a propagating explosion and the death toll would have been significantly less."

Massey’s safety hazards were not recorded, or were incorrectly recorded, because its pre-shift and on-shift examination system had effectively broken down, the report found.

Federal and state regulators did not blame either and were criticized for "failing to use all the tools at their disposal".

MSHA did not ensure the company complied with federal laws on safety and the West Virginia Office of Miners' Health Safety and Training could not live up to its role of watchdog for coal miners and did not enforce state laws.

"Despite MSHA's considerable authority and resources, its collective knowledge and experience, the disaster at the Upper Big Branch mine is proof positive that the agency failed its duty as the watchdog for coal miners," the report said.

Independent investigator McAteer – who was appointed by then-state governor Joe Manchin last April to review the blast that killed 29 Massey Energy workers – carried out an exhaustive study that included physical examinations of the mine, regulatory records, the mine's internal records and more than 300 interviews with current and former mine employees, family members of miners, as well as with state and federal mine regulators.

Massey Energy executives invoked the Fifth Amendment to avoid giving evidence to the report.

In a statement to CNN, Massey Energy general counsel Shane Harvey said the company was reviewing the report carefully and agreed the industry needed to examine whether it could achieve better methane monitoring technology.

He is reported as saying that he disagrees with the report’s conclusion that the explosion was fuelled by coal dust.