Check for updated news on Coal Tattoo. CHARLESTON, W.Va. -- Federal officials announced Tuesday that they had expanded their investigation the Upper Big Branch Mine Disaster to allow workers and families of the victims to anonymously discuss concerns about the Massey Energy mine "without fear of retaliation."Labor Secretary Hilda Solis called for the move, which involved formation of a "supplemental investigation group" in addition to the U.S. Mine Safety and Health Administration's primary investigation team.Robert Phillips, a 27-year MSHA veteran who recently retired, will be charged with providing a "safe, confidential venue for the general public, family members of the victims and miners to speak freely to MSHA investigators," said an agency news release."We need to use every available tool to establish the cause of this tragedy that took 29 coal miners' lives," said MSHA chief Joe Main. "The work of this special team will be part of MSHA's investigative process, and it will give family members and others the opportunity to share information they might otherwise not feel comfortable passing along."MSHA also announced Tuesday that the manager of its coal mine safety and health office in Wilkes-Barre, Pa., would be in charge of conducting an "internal review" of MSHA actions before the April 5 explosion at the Upper Big Branch Mine.At the same time, MSHA has scheduled a meeting for Wednesday night with families of the 29 miners killed at Upper Big Branch, and is expected to give the families more details of how its investigation into the disaster will proceed. A public announcement of those details is expected Thursday.Main has been under increasing pressure to conduct witness interviews and other portions of the MSHA investigation through a hearing that would be open to the general public and the media. The United Mine Workers union has called for such a hearing, as has a collection of media organizations, including The Charleston Gazette. At least two widows have also asked for a public hearing.Investigators believe the huge explosion was caused by the ignition of methane and probably made far worse by accumulations of coal dust.Federal and state officials have delayed going back underground to gather evidence because sampling has found gases that could indicate there is an ongoing fire. Massey is pumping nitrogen into the mine to put out the fire, but officials have said privately it could be several months before it is safe for teams to re-enter the mine.Witness interviews in such investigations have generally been conducted in private, but with coal company lawyers often being allowed in the room.Interviews in the Upper Big Branch probe have been repeatedly delayed, and were postponed again Tuesday as MSHA struggles to sort out how to proceed."We are waiting for MSHA to decide if hearings will be private or public," said Jama Jarrett, a spokeswoman for the state Office of Miners Health, Safety and Training.Reach Ken Ward Jr. at email@example.com or 304-348-1702.