CHARLESTON, W.Va. -- Massey Energy on Friday continued to disagree with findings of the federal government's investigation into the explosion that killed 29 workers at the company's Upper Big Branch Mine in Raleigh County. Massey officials told families of the miners, and then media representatives, that they don't believe worn-out bits on a mining machine, broken water sprays or a buildup of explosive coal dust contributed to the Upper Big Branch disaster. "We just look at the evidence a different way, I guess," Massey general counsel Shane Harvey said during a telephone media briefing Friday morning. Massey held the media briefing at the same time it continued a closed-door meeting with families of the miners, and a week after the U.S. Mine Safety and Health Administration offered its most detailed discussion of the evidence so far gathered in the mine disaster probe. MSHA officials and the independent investigators appointed by Gov. Joe Manchin believe the explosion involved an ignition of methane that was then made more powerful -- and spread through the mine -- by a buildup of highly explosive coal dust. "The science supports the conclusion that coal dust was involved in this explosion," said Davitt McAteer, who is leading the independent probe. Since the disaster, Massey has engaged in a heated public-relations effort to challenge the MSHA probe and to lay the groundwork for its legal defense in wrongful-death cases by the miners' families. At the same time, MSHA has harshly criticized Massey's safety practices and federal prosecutors have said they are investigating potential criminal violations dating back more than four years at Upper Big Branch. MSHA investigators had said they believed the "most likely" ignition source for the explosion was bit on the longwall mining machine's cutting tool, or shearer. Agency officials showed family members and the media photograph of one worn bit, emphasizing how without a fresh carbide tip the bit would be more likely to spark when it cut into mine rock. Massey officials went directly after that argument, distributing a photo showing the rest of the longwall shearer's bits, and saying that only two of the unit's 44 bits showed the sort of wear in the photo MSHA released. The company also repeated its previous position that missing water spray nozzles did not contribute the explosion. In a prepared response, MSHA said its investigators are "still reviewing evidence to determine the total number of bits with excessive wear." "Water sprays were not working behind each of the bits on the tail-drum as required, because some of the sprays had been totally removed and the required pressure on each spray could not be maintained," MSHA said. "That being said, it takes only one bit without proper spray to allow an ignition to occur." Massey also repeated its argument that a crack in the mine floor allowed a huge amount of methane to flood the mine, and that it was methane -- and not coal dust -- that fueled the powerful explosion. But MSHA officials and McAteer have said physical examinations of the mine found no evidence of such a large methane blast, especially in the area of the floor crack. MSHA has said that it found widespread violations throughout the mine of requirements that mine operators spread crushed limestone, or "rock dust," to keep coal dust from igniting. Massey on Friday repeated its believe that the MSHA sampling would be thrown out in court, as similar sampling was following a 2001 explosion that killed 13 miners in Alabama. But McAteer and MSHA pointed out that conditions in the Alabama mine were much different than at Upper Big Branch, and played a major role in MSHA losing that legal case. "The numerous differences at UBB include: different coal seam, no roof fall before, one explosion rather than two, not much rib sloughage, and only a small area of the mine was flooded," MSHA said in its statement. At least one family member expressed frustration at the conflicting reports following Massey's meeting. "They're really just contradicting each other," Clay Mullins, whose brother Rex died in the explosion, told The Associated Press. Massey "put on a good show and had a lot of information to discuss," Mullins said, "... But I would have to lean toward MSHA. I think it's more an accumulation of dust." Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.