JOHN RABYBECKLEY, W.Va. (AP) â¿¿ The former superintendent of a southern West Virginia mine where an explosion killed 29 workers pleaded guilty Thursday to a federal fraud charge. Gary May of Bloomingrose, the highest-ranking Massey Energy official charged in connection with the blast, faces up to five years in prison when sentenced Aug. 9. May pleaded guilty before U.S. District Judge Irene Berger in Beckley to conspiracy to defraud the federal government. The charge stems from his actions at the Upper Big Branch mine. Prosecutors said May manipulated the mine ventilation system during inspections to fool safety officials and disabled a methane monitor on a cutting machine a few months before the explosion on April 5, 2010. It wasn't clear from court papers whether the device was ever fixed. The blast was the worst U.S. mining disaster in 40 years. Prosecutors have accused Massey of violating a host of safety laws out of a desire to put production and profits first. Three investigations of the tragedy concluded that the company allowed highly explosive methane and coal dust to build up inside the mine, where it was ignited by a spark from an improperly maintained piece of cutting equipment. Clogged and broken water sprayers then allowed what could have been just a flare-up to become an epic blast, the investigations found. May spoke in quiet tones and gave short answers until Berger asked him to describe what happened in relation to the charge. "When an inspector would show up on the property, I would call up and let them know that an inspector was wanting to come underground," May said. "It was my intention to let them know that someone was coming." Berger also asked May if he acted with anyone else. "All the station foremen, they would call up periodically, to ask if there were any inspectors," May replied.