CHARLESTON, W.Va. -- Massey Energy's board of directors vowed Thursday to stick by company CEO Don Blankenship, while federal and state investigators revealed potentially dangerous conditions may delay for a month or more the underground portion of their probe into the worst U.S. coal-mining disaster in 40 years.Bobby R. Inman, a former Navy and CIA officer, issued a statement on the board's behalf in his role as the "lead independent director" of the Richmond, Va.-based coal giant."The Massey Energy family continues to grieve for those lost in the awful tragedy at Upper Big branch and remains fully committed to the safety or our members," Inman said."During times like these, a change in senior management is not appropriate or in the best interest of our members and shareholders," Inman said. "Therefore, we want to emphasize that Don Blankenship has the full support and confidence of the Massey Energy Board of Directors."Inman issued the statement just after Blankenship vigorously defended Massey's safety record in a conference call with industry financial analysts, and as the company was hit with a second lawsuit by shareholders alleging Massey management has ignored growing safety problems."Massey's management has been well aware of safety issues, but has chosen to drive the company toward higher coal production regardless of the cost to its workers' health and safety," says the suit filed Wednesday in Wyoming County Circuit Court on behalf of the International Union of Operating Engineers Pension Fund, which owns Massey stock.Last week, a similar suit was filed against Massey and its board by another stockholder group. One Massey board member, Lady Barbara Thomas Judge, resigned earlier this week, but did not publicly state a reason for the move.In that case, Kanawha Circuit Judge Jim Stuckey on Thursday ordered Massey directors to appear in court next month to explain why they should not be held in contempt for violating a previous settlement to improve oversight of Massey's workplace safety performance.Massey is under intense scrutiny from state and federal regulators and the national media, following the huge underground explosion that killed 29 workers at the Upper Big Branch Mine in Raleigh County on April 5.Mine safety experts have said preliminary indications are that the explosion involved an ignition of methane gas that was made far worse by accumulations of highly explosive coal dust in the mine. Massey had been cited repeatedly for ventilation violations and coal dust accumulations prior to the explosion.During Thursday's conference call with stock analysts, Blankenship defended the company's safety record in response to several questions about the explosion and media coverage of repeated violations at Upper Big Branch."Obviously, I don't want to speculate, but either something went wrong from a natural/unnatural manner that was not foreseeable by us or human beings or somebody made a mistake or something," Blankenship said. "We don't know."It's not due to us not being focused on safety, not having a strong safety culture, not putting safety first. Some of the implications have been that we don't focus on safety or we put dollars in front of safety and nothing could be further from the truth."Still, state and federal regulators confirmed Thursday they planned to investigate reports from several Upper Big Branch widows that miners at the operation were sent home on April 2, the Friday before the explosion, because of "bad air" in the mine."We were not made aware of any evacuation on April 2 and will investigate this report," said Jama Jarrett, spokeswoman for the state Office of Miners' Health, Safety and Training.Amy Louviere, spokeswoman for the U.S. Mine Safety and Health Administration, said MSHA was also not notified of any ventilation issues at the mine that day or any evacuation. MSHA did not have an inspector at the mine that day, she said."The team will follow up on every one of these complaints," Louviere said.Louviere also said Thursday that air quality tests of the Upper Big Branch Mine turned up the presence of ethylene and acetylene, both gases that could indicate a fire is burning somewhere underground."So, until they figure out exactly what the source of these gases is, the teams will not be allowed to go underground," Louviere said.Jarrett said it could keep investigators out of the mine for another month or so.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.