CHARLESTON, W.Va. -- Federal officials investigating the Upper Big Branch Mine Disaster have cited Massey Energy for improper storage of explosives in the underground mine, government documents and a company regulatory filing confirmed Monday.U.S. Mine Safety and Health Administration officials accused Massey of creating an "imminent danger" of death or serious physical injuries in an enforcement order issued in late July and made public Monday.MSHA investigators discovered a 2-by-2-by-3 foot box labeled "explosives" in a conveyor belt tunnel in the Raleigh County mine, according to agency documents. The area where the box was found was "predominantly dry," but the bottom "had moisture on it.""This condition exposes all miners who work underground to the hazards associated with handling deteriorated explosives," MSHA said in its enforcement order.It was not clear on Monday exactly what the explosives were used for at Upper Big Branch, and Massey said the MSHA enforcement action had nothing to do with the April 5 explosion that killed 29 workers at the mine.The Charleston Gazette asked for a copy of the July 30 MSHA enforcement order more than two weeks ago, on Aug. 6, after a brief notation about its existence appeared on the agency's online database.A copy was made public by MSHA on Monday. MSHA did not immediately respond to requests for comment beyond what the order itself said.Also Monday, Massey filed a disclosure with the U.S. Securities and Exchange Commission making note of the enforcement order. Massey had not included the order in summary enforcement statistics filed with the SEC on Aug. 9.That filing, covering the quarter from April through June, was the first under a new federal law that requires coal operators to inform the SEC and their shareholders about safety and health violations.In its Monday SEC filing, Massey said the "locked box of explosives was brought to the surface" the same day MSHA issued its order and was "removed from the mine property and disposed of.""The condition cited in the [MSHA] order did not relate to the April 2010 Upper Big Branch tragic accident," Massey said in its filing.Ron Wooten, director of the state Office of Miners Health, Safety and Training, said he was not familiar with the MSHA enforcement action and was not sure exactly what the explosives were used for at Upper Big Branch.Wooten said the explosives could have been used in construction of certain types of ventilation controls, called overcasts, or in breaking up rock.