CHARLESTON, W.Va. -- U.S. Attorney Booth Goodwin said Wednesday that his office expects to bring more criminal charges related to its Upper Big Branch Mine Disaster investigation, and that action in the probe will come "very shortly."Goodwin did not provide specifics, but said the investigation remains in a "critical phase" as prosecutors try to move up the corporate ladder among individuals who ran Massey Energy Co."We're advancing as quickly as we can in that regard, and I anticipate we will have some future announcements very shortly," Goodwin said.Goodwin discussed the matter Wednesday afternoon outside the first meeting of a panel appointed to dole out $48 million Alpha Natural Resources provided for mine safety and health research as part of a deal to avoid corporate criminal prosecution for the Upper Big Branch explosion.In December, Goodwin and his team secured a $209.5 million settlement with Alpha Natural Resources, which acquired the Upper Big Branch Mine when it bought Massey Energy.Goodwin agreed not to prosecute the company for any Upper Big Branch criminal liabilities, but required Alpha to spend $80 million during the next two years on mine safety improvements and create a $48 million mine safety research trust fund. Alpha also agreed to pay $46.5 million in restitution to families of the disaster victims and $35 million to resolve pending Massey safety fines, including $10.8 million levied for violations related to the Upper Big Branch explosion.The settlement with Alpha, however, did not prohibit prosecutors from pursuing charges against any individuals -- including Massey officers, employees or agents -- who played a role in the mine disaster.Federal, state and independent investigations have blamed the worst U.S. coal-mining disaster in nearly 40 years on widespread safety violations, including a systematic failure by Massey management to comply with rules aimed at controlling the buildup underground of explosive coal dust.Prosecutors continue to dig into the April 5, 2010, blast that killed 29 miners and to examine other safety practices at other Massey operations across Southern West Virginia."We're still advancing as quickly as we can," Goodwin said. "Our investigation has been fairly broad in its scope, so it takes some time."So far, Goodwin's office has brought charges against three people linked to the Raleigh County mine where the explosion occurred.Thomas Harrah, a former miner at the site, was sentenced to 10 months in jail after he admitted to faking a foreman's license when he performed key mine safety examinations at the mine between January 2008 and August 2009 and then lying to investigators about his actions.Former Massey Energy security director Hughie Elbert Stover is appealing a three-year jail sentence he received after being convicted of lying to investigators and trying to destroy evidence about Massey's practice of warning underground workers of impending government inspections.And former Upper Big Branch mine superintendent Gary May is awaiting sentencing after pleading guilty to plotting "with others known and unknown" to put coal production ahead of worker safety and to conceal the resulting hazards on numerous occasions at Upper Big Branch. May admitted that he took part in a scheme to provide advance warning of government inspections and then hide or correct violations before federal agents could make it into working sections of the mine.U.S. District Judge Irene Berger has twice postponed May's sentencing -- now scheduled for mid-January -- after prosecutors said they needed more time to get information from May, who is cooperating with the ongoing investigation as part of a plea deal.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.