CHARLESTON, W.Va. -- Federal and state investigators began closed-door interviews Monday in their probe of the Upper Big Branch Mine disaster, as a federal judge considered a suit filed by the United Mine Workers and two disaster victims who want the questioning done during a public hearing.

Officials from the U.S. Mine Safety and Health Administration and the state Office of Miners Health Safety and Training began by privately questioning some of their own inspectors who had visited the Massey Energy mine in Raleigh County prior to the April 5 explosion that killed 29 workers.

In their suit seeking public sessions, lawyers for the UMW and the families of miners William Griffith and Ronald Maynor argued, among other things, that the closed-door interviews allow regulators to avoid difficult questions about the performance of government agencies charged with protecting miners.

"Without the participation of miners' representatives in the accident investigation interviews, MSHA's analysis of its own role, if any, will remain secretive and inherently suspect," states the lawsuit, filed against MSHA chief Joe Main Monday in federal court in Charleston.

U.S. District Judge Irene C. Berger did not immediately rule or schedule a hearing on the suit's request for a temporary restraining order to stop the interviews until the case could be more fully argued.

The suit asks Berger to require MSHA to allow the miners' families and the UMW -- which was appointed as official miners' representative by several workers at the non-union mine -- to sit in on witness interviews. It also asks that Berger order the entire investigation conducted as a public hearing.

"We believe it is imperative for the families of the victims of this tragedy to be able to hear the evidence that will be gathered in these interviews for themselves," said UMW President Cecil Roberts.

"We also believe that the workers -- who will have to go back to work in that mine -- must be allowed to have their designated representatives in the interviews, asking questions and hearing testimony first-hand."

Last week, the Obama administration rejected calls from the UMW, miners' families, Massey Energy and the news media for a completely public investigation.

Officials from the U.S. Mine Safety and Health Administration and the state Office of Miners Health Safety and Training began by privately questioning some of their own inspectors who had visited the Massey Energy mine in Raleigh County prior to the April 5 explosion that killed 29 workers.

In their suit seeking public sessions, lawyers for the UMW and the families of miners William Griffith and Ronald Maynor argued, among other things, that the closed-door interviews allow regulators to avoid difficult questions about the performance of government agencies charged with protecting miners.

"Without the participation of miners' representatives in the accident investigation interviews, MSHA's analysis of its own role, if any, will remain secretive and inherently suspect," states the lawsuit, filed against MSHA chief Joe Main Monday in federal court in Charleston.

U.S. District Judge Irene C. Berger did not immediately rule or schedule a hearing on the suit's request for a temporary restraining order to stop the interviews until the case could be more fully argued.

The suit asks Berger to require MSHA to allow the miners' families and the UMW -- which was appointed as official miners' representative by several workers at the non-union mine -- to sit in on witness interviews. It also asks that Berger order the entire investigation conducted as a public hearing.

"We believe it is imperative for the families of the victims of this tragedy to be able to hear the evidence that will be gathered in these interviews for themselves," said UMW President Cecil Roberts.

"We also believe that the workers -- who will have to go back to work in that mine -- must be allowed to have their designated representatives in the interviews, asking questions and hearing testimony first-hand."

Last week, the Obama administration rejected calls from the UMW, miners' families, Massey Energy and the news media for a completely public investigation.

MSHA plans several staged public events later, but is conducting the key witness interviews in private. Despite the suit, interviews are scheduled to continue through the week. The private sessions are being held at the National Mine Health and Safety Academy outside Beckley.

"There are both public and private components to any law enforcement investigation," MSHA spokeswoman Amy Louviere said in a prepared response to questions. "Ultimately, this investigation will represent the most open process the agency has ever established."

Investigators believe, based on preliminary information, that the huge explosion was caused by the ignition of methane gas and probably made far worse by a buildup of highly explosive coal dust in the Upper Big Branch Mine.

The 29 deaths rank it as the worst U.S. coal-mining disaster in 40 years.

Also Monday, the U.S. House Labor Committee announced it would hold a field hearing on the disaster May 24 in Beckley. Family members of some of miners killed in the explosion at a Massey Energy mine in Raleigh County are expected to testify. The hearing will start at 9 a.m. at the Robert C. Byrd U.S. Courthouse.

Meanwhile, Massey and its CEO, Don Blankenship, continued their criticism of federal regulators, releasing a letter Blankenship sent to MSHA last week complaining that the agency had forced Massey to turn off nearly half of the air-cleaning scrubbers installed on its continuous mining machines in underground mines.

In response, MSHA issued a statement that said, "This is an issue we're looking at very closely. We plan to sit down with [the National Institute for Occupational Safety and Health] in the near future to discuss next steps."

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