CHARLESTON, W.Va. -- A federal judge has again postponed the sentencing of a former Upper Big Branch Mine superintendent, after prosecutors said the delay would assist their ongoing criminal investigation of the April 2010 mine disaster that killed 29 workers.U.S. District Judge Irene Berger has rescheduled the sentencing hearing for Gary May for Jan. 17. The sentencing had been set for Oct. 4 in Beckley, after being delayed from earlier this month.Earlier this week, Assistant U.S. Attorney Steve Ruby said in a court filing that May "is cooperating in an ongoing investigation and the parties need additional time to fully develop the extent of his cooperation."Ruby added, "The additional time sought ... will allow significant further development of the investigation" into the April 5, 2010, explosion at a Massey Energy mine in Raleigh County.In a plea deal with prosecutors, May admitted that he plotted "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.For example, May, after learning that federal Mine Safety and Health Administration inspectors were about to sample the level of coal dust in the mine, "surreptitiously redirected" additional fresh air to the area to conceal actual working conditions in the mine.May also "caused and ordered" the disabling of a methane monitor on a continuous mining machine at Upper Big Branch less than two months before the deadly blast.May also ordered an unnamed person to falsify mine examination records by omitting a hazardous condition -- high water that could endanger workers and interfere with the flow of fresh air through underground tunnels.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.The delay in May's sentencing puts that matter on a similar timeline to the delay Berger ordered in a civil case filed by former Massey shareholders who say the company lied to them about its safety record.In July, when prosecutors asked Berger to force that delay in the civil case, they said the criminal investigation of the mine disaster "is in a critical period, developing valuable information that became available only recently."So far, May is the third person to be charged in the federal criminal investigation at Upper Big Branch.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.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.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.