The company noted that the readings were almost three times over normal liberation rates for UBB.

Readings were taken from the mine’s primary ventilation exhaust, the Bandytown Fan, by the US Mine Safety and Health Administration.

Massey said that the information received demonstrates several points – the first being that the unexpected methane release was overwhelming to normal safety operations.

“To put it in perspective, a methane release of this size would completely fill a 2000-square-foot house with an explosive atmosphere in under 40 seconds, and could fill the volume of a typical mine entry to explosive levels in under 25 seconds,” explosions expert and Massey UBB investigation team member Dr Christopher Schemel said.

“While the UBB investigation is still ongoing, and it is far too early to determine the exact cause of the April 5 accident, the methane gas data is a very important piece of evidence.”

Another important factor in the data is that ventilation system fans at the operation continued to operate even after the explosion and continued to supply fresh air at a rate outlined by federally-mandated design specifications.

“Gas samples taken by MSHA from the Bandytown ventilation fan show the mine atmosphere experienced a rapid inundation of methane, raising the concentration in the ventilation air significantly,” the company said.

“Furthermore, the ventilation gas reading data details how the mine environment returned to more normal conditions a few days later.”

The data MSHA collected from UBB has been made available online through Massey’s website.

On Thursday afternoon, federal officials from MSHA said they believed the figures referred to in their announcement were taken several hours after the explosion, during rescue and recovery efforts relating to the incident.

“This information was shared with Massey some time ago,” the agency said.

“Elevated methane levels after an explosion in a mine would be expected if the explosion damaged ventilation controls and if mine gasses from sealed areas or from the longwall gob were pulled into the ventilation air current. This would cause a rise in methane after the explosion and could account for elevated methane in the samples.”

MSHA also noted that it will obviously be evaluating methane levels closely as part of the UBB blast investigation, but that explosions require concentrations of gas or dust along with a source of ignition.

“Massey’s ventilation plan, when properly followed, provided large quantities of air across the longwall face to keep methane and dust levels below combustible levels,” federal officials said, pointing out that regulations also require functioning methane detectors to power off mining equipment before methane levels become combustible so as to eliminate that potential ignition source.

“We know this company and this mine violated ventilation standards multiple times in the months leading up to the explosion. We’ll look closely at the methane levels, whether Massey was following its plan at the time of the explosion, and any evidence indicating methane detectors were tampered with.”

In related UBB news, Massey chief executive officer Don Blankenship said in a televised interview that federal regulations over the coal industry are “excessive” and the government’s technical expertise is lacking.

“The feeling of the industry is that we’re regulated too much and not too little,” he told Bloomberg Television’s InBusiness.

“Tragedies lead to more regulation.”

He also noted that miner safety was put at risk by that increased regulation, as engineers for the coal industry are at a higher level than those working for government agencies.

“It basically comes down to engineers that work for the company that we believe are more technically competent than those that work for the government,” he said.