Officials had initially assumed that the source of the methane was the Lower Eagle Seam, which lies below the Eagle Seam at vertical distances that vary form five to 25 feet.

But further investigation determined that, "The Lower Eagle Seam may simply represent an impermeable cap-rock for a larger gas trap," according to the MSHA documents.

"Natural gas may be ponded in structural highs beneath the Lower Eagle Seam, after rising into domes and subsequently being trapped from further rise by relatively impermeable coal or shale," according to one MSHA report, dated May 4, 2004.

Another MSHA reported, dated July 15, 2004, concluded that, "methane trapped in zone below the Eagle Coal Seam could be released into the mine through fractures opened by longwall coal extraction."

That memo, written by several MSHA staffers for then-acting District Manager Stephen Gigliotti, was prepared to summarize a May 26, 2004, meeting where agency officials and Massey representatives discussed the problem and outlined possible solutions.

Previously, Massey had told MSHA the company planned to drill degasification wells into the Lower Eagle Seam prior to subsequent longwall mining "in an attempt to decrease the potential for future outbursts." MSHA concluded, "This appears to be a reasonable plan."

After the May 2004 meeting, MSHA outlined a variety of other potential steps, including increased airflow to help sweep any methane out of the mine, better training for miners to be aware of warning signs of an impending methane outburst, and a plan for sealing off portions of the mine floor where fractures and methane leaks were likely to occur.

None of the MSHA documents indicate what, if any, of these steps were ultimately taken by the company or mandated by the agency.

Shane Harvey, Massey's general counsel, said the company is reviewing the matter.

"We are looking at it," Harvey said. "I don't know the details of what was done."

MSHA records appear to indicate that Massey was cited for a minor violation of its ventilation plan after the 2004 incident. The company paid a $525 fine. Agency records do not appear to contain any citations for the 2003 incident.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.

No one was injured. But it wasn't the first time such an incident, known as a "methane outburst" occurred at the Raleigh County mine.

Less than a year before, on July 3, 2003, Massey had reported that Upper Big Branch became inundated with methane after an "extreme bump" and heaving of the mine floor.

"Mine personnel described the July 2003 outburst as a very high pressure event, comparable to the sound of a jet engine," according to an internal U.S. Mine Safety and Health Administration report on the incident.

Federal regulators concluded at the time that a reservoir of natural gas below the Upper Big Branch Mine might easily be released into the active mining operation. They recommended a series of steps to try to prevent such incidents, or at least to control them, hopefully preventing an explosion or fire. One such recommendation -- to drill "degasification" wells into the mine -- was among the steps Massey Energy President Don Blankenship argued this week was the wrong approach for ventilating Upper Big Branch.

MSHA documents describing the 2003 and 2004 incidents, obtained this week by The Charleston Gazette, are being closely reviewed by government teams who are investigating the Upper Big Branch Mine Disaster. Investigators are also trying to find additional records that might explain what actions were taken by MSHA and Massey after the incidents.

"That is a good question, and it's a question I've asked our investigators," said Ron Wooten, director of the state Office of Miners Health, Safety and Training. "Were the recommendations put in place? What was done? Those are the questions that need to be answered."

Jesse Lawder, a spokesman for MSHA, said the agency would not comment on the 2003 and 2004 incidents or on what actions it required Massey to take afterward.

Twenty-nine miners died and two others were injured in an April 5 Upper Big Branch explosion, which investigators believe involved an ignition of methane gas made far worse by a buildup of highly explosive coal dust.

MSHA and the state are conducting closed-door interviews of government inspectors, Massey workers and company officials as they continue their probe into the worst U.S. coal-mining disaster in 40 years. While former Upper Big Branch miners and the families of some of the disaster victims are speaking out about safety problems at the mine, government officials will say little publicly about what they are learning in their investigation.

While Massey has publicly said air quality in the mine was good just prior to the explosion, government inspection reports include repeated violations for poor airflow, ignoring mandated ventilation requirements, broken methane monitors and other problems that could play a role in an explosion or fire.

And investigators are now concerned that the previous methane outbursts could provide one possible explanation for where the explosive gases came from that ignited the April 5 explosion.

Methane is released naturally from coal seams during the mining process, and is a constant threat in underground coal operations. Federal law requires all mines to operate according to MSHA-approved ventilation plans intended to sweep fresh air through a mine, and keep coal dust and methane below explosive levels. Ventilation plans include requirements for large fans and a series of walls, curtains and other devices to direct fresh and dirty air in and out of underground tunnels.

The 2003 and 2004 methane outbursts occurred as Massey's Performance Coal Co. was mining different "panels" of coal with its advanced longwall mining machine. But both incidents occurred as the company continued to mine -- as it was still doing prior to the April explosion -- in a coal vein known as the Eagle Seam.

Officials had initially assumed that the source of the methane was the Lower Eagle Seam, which lies below the Eagle Seam at vertical distances that vary form five to 25 feet.

But further investigation determined that, "The Lower Eagle Seam may simply represent an impermeable cap-rock for a larger gas trap," according to the MSHA documents.

"Natural gas may be ponded in structural highs beneath the Lower Eagle Seam, after rising into domes and subsequently being trapped from further rise by relatively impermeable coal or shale," according to one MSHA report, dated May 4, 2004.

Another MSHA reported, dated July 15, 2004, concluded that, "methane trapped in zone below the Eagle Coal Seam could be released into the mine through fractures opened by longwall coal extraction."

That memo, written by several MSHA staffers for then-acting District Manager Stephen Gigliotti, was prepared to summarize a May 26, 2004, meeting where agency officials and Massey representatives discussed the problem and outlined possible solutions.

Previously, Massey had told MSHA the company planned to drill degasification wells into the Lower Eagle Seam prior to subsequent longwall mining "in an attempt to decrease the potential for future outbursts." MSHA concluded, "This appears to be a reasonable plan."

After the May 2004 meeting, MSHA outlined a variety of other potential steps, including increased airflow to help sweep any methane out of the mine, better training for miners to be aware of warning signs of an impending methane outburst, and a plan for sealing off portions of the mine floor where fractures and methane leaks were likely to occur.

None of the MSHA documents indicate what, if any, of these steps were ultimately taken by the company or mandated by the agency.

Shane Harvey, Massey's general counsel, said the company is reviewing the matter.

"We are looking at it," Harvey said. "I don't know the details of what was done."

MSHA records appear to indicate that Massey was cited for a minor violation of its ventilation plan after the 2004 incident. The company paid a $525 fine. Agency records do not appear to contain any citations for the 2003 incident.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.