CHARLESTON, W.Va. -- A plea hearing for a longtime Massey Energy executive who is cooperating with a federal investigation of the company's safety practices has been scheduled for mid-January.At the same time, prosecutors also are seeking to delay the sentencing of a former Upper Big Branch Mine superintendent, saying they need more time to glean information from him in their ongoing probe of the April 2010 explosion that killed 29 miners.Former Upper Big Branch superintendent Gary May is scheduled to be sentenced Jan. 17 after he pleaded 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 the Raleigh County mine. 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.In a court filing, Assistant U.S. Attorney Steve Ruby asked for a four-month delay because May "continues to provide important cooperation in an ongoing criminal investigation."Already, U.S. District Judge Irene Berger has twice postponed May's sentencing 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."Notable progress has been made in the investigation since this sentencing proceeding was last continued," Ruby wrote. "The further continuance requested here will allow that progress to be extended and will avoid any risk to the investigation from the sentencing proceeding itself."On Tuesday, Berger scheduled a plea hearing for longtime Massey official David C. Hughart for Jan. 16 in Beckley. Hughart has agreed to plead guilty to two criminal charges and provide testimony about a decade-long conspiracy to defy safety laws and hide the resulting conditions from government inspectors.Hughart, 53, of Crab Orchard, could face up to six years in federal prison. May faces up to one year in prison for one felony charge.Reach Ken Ward Jr. at email@example.com or 304-348-1702.