CHARLESTON, W.Va. -- Federal mine safety officials are refusing to make public documents that may turn out to contain crucial information regarding potential ventilation problems in the weeks prior to the explosion that killed 29 miners at Massey Energy's Upper Big Branch Mine.U.S. Mine Safety and Health Administration officials have not responded to public records requests for the documents and have so far refused to provide them to an independent team investigating the mine disaster at the request or former Gov. Joe Manchin.The documents in question detail five proposed ventilation changes that Massey sought from MSHA in March 2010, but that were still awaiting federal agency action when the explosion occurred on April 5.The records also outline more than a dozen ventilation changes that Massey proposed and MSHA denied between September 2009 and April 2010, according to a document index made public last week.MSHA officials have not technically denied a Gazette Freedom of Information Act request for the ventilation documents, but have also not explained their reasons for not having made them public nearly a year after the disaster.Members of the independent state team, headed by longtime mine safety advocate Davitt McAteer, have been stonewalled for months as they've tried to get the records and wrap up their investigation report before the one-year anniversary of the blast."We don't have those records," McAteer said Thursday. "We have asked for copies of those documents. We think they address a number of questions that have been raised about the ventilation plans and MSHA's role in approving or denying the ventilation plans."Under state and federal laws, mine operators are required to ensure that enough fresh air flows into underground mines to protect miners from dangerous fumes and dust and to prevent a buildup of methane gas or dust than can cause explosions and fires.Mine operators submit detailed ventilation plans to MSHA, and those plans must receive agency approval before they can be put into action and before mines are allowed to legally operate.Massey officials have repeatedly complained that MSHA officials dictated that they make ventilation changes the company's engineers didn't believe were safe. MSHA has responded that it's up to a mine operator to propose a workable and safe ventilation plan.Federal and state investigators believe that the Upper Big Branch disaster involved a methane explosion that was made far worse by a buildup of highly explosive coal dust underground. Still not explained, though, is what if any role problems with the mine's ventilation system played in the explosion.MSHA inspectors had cited the company with a variety of serious ventilation violations in the months before the blast. Massey also was in the process of switching away from the use of a conveyor belt tunnel to bring fresh air into the mine because the company had decided it didn't want to submit a detailed plan justifying the practice or add new safety equipment required by a new MSHA rule on so-called "belt air" ventilation.In the months after the explosion, MSHA posted dozens of documents about Upper Big Branch on its Web site, including inspection reports and other enforcement records. MSHA also posted the mine's basic ventilation plan and a variety of changes that MSHA had approved. But the agency has not posted any of the proposed changes that MSHA denied or any of the proposals that had not been acted on at the time of the explosion.During a conference call with reporters Thursday, Main initially blamed the ongoing criminal investigation of the mine disaster on his agency's failure to produce the ventilation documents."There is a normal course of collecting and controlling information and the agency has to have some ability to conduct its business in a way that serves what the Mine Act calls for," Main said.Asked if prosecutors had specifically asked MSHA not to release the ventilation records, Main said he wasn't sure what ventilation records had not been made public."You may know more about it than I do," Main said. "I know there have been some requests and we're proceeding with processing those. I don't know exactly what files you're talking about. I'll have our folks take a look at it."Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.