Following the release, MSHA also announced it has fined the operation $US336,000 for six violations relating to the miners’ deaths – including two for reckless disregard and three for negligence – with all classified as S&S (significant and substantial). Its report on the incident was released late Thursday following the agency’s briefing of the document to the late miners’ families at a gathering in Harlan, Kentucky.

It was “violations of mandatory mine safety laws” that ultimately led to the accident, according to agency assistant secretary Richard Stickler.

Specifically, it illustrated the events of May 20 in its 64-page report, focusing on the torch’s improper use: “An explosion … occurred … in a sealed area of the mine. MSHA investigators determined that the explosion occurred when a mine official, who was accompanied by one miner, cut metal straps extending through seals with an acetylene torch, igniting explosive levels of methane that accumulated in the sealed area.

“The two miners located near the seals died immediately, and three miners trying to evacuate the mine after the explosion died from carbon monoxide poisoning. One miner was rescued while escaping from the mine.”

The report cited the mine’s management crew as responsible for the deaths that followed the explosion due to a myriad of negligent acts: “Mine management failed to ensure that proper seal construction procedures were utilized in the building of the seals behind which the explosion occurred [and] also failed to ensure that safe work procedures were used while employees attempted to make corrections to an improperly constructed seal.

“Furthermore, mine management failed to adequately train miners in escapeway routes. Finally, mine management failed to adequately train miners in the proper use of self-contained self-rescuers.”

To develop its analysis of the events, MSHA outlined varied aspects of the mine’s infrastructure and practices, such as development, ventilation, roof control, escapeways and emergency evacuation, drills, maps, rock dusting, seal construction, and the origin, flame and forces involved with the torch and ignition of the explosion. The mine’s electrical equipment, mantrips, cap lamps, detectors and training protocols were also reviewed.

The six violations making up Darby’s $336,000 fine were as follows:

30 CFR 75.333(h), S&S, Reckless Disregard – Seal Integrity;

30 CFR 75.1106, S&S, Reckless Disregard – Inadequate methane testing;

30 CFR 75.370(a)(1), S&S, Reckless Disregard – Improper Omega block seal construction;

30 CFR 75.383(a), S&S, High Negligence – Missing escapeway identification on maps at surface and underground;

30 CFR 75.383(b)(1) S&S, High Negligence – Inadequate training for drills using alternate escapeways; and

30 CFR 48.8(b)(8); S&S, High Negligence – Insufficient required annual refresher training for miners.

Stickler said in a statement Friday that the agency appreciated the cooperation received from the miners’ families during its examination of the incident.

“We at MSHA extend our thoughts and prayers to the families for their losses, and we thank them for their patience as we worked to complete our investigation,” he said.

The Darby explosion took the lives of Jimmy Lee, 33, and Amon Brock, 51, who both died from blunt force trauma and heat injuries. Roy Middleton, 35, Bill Petra, 49, and Paris Thomas Jr, 53, were all found to have succumbed to carbon monoxide poisoning and smoke inhalation.