Associated Press Miners' helmets and painted crosses sit at the entrance to Massey Energy's Upper Big Branch coal mine in Montcoal, W.Va., in April, a year after the explosion. 
 
 Massey Energy Co. could have prevented the West Virginia mine explosion that killed 29 workers last year and the company failed to disclose some hazards in reports it provided to government inspectors, federal safety officials said Wednesday. 
 
 Patricia Smith, the U.S. Labor Department's top lawyer, said not recording hazards where required was a potential criminal violation of the Mine Act and "we have notified the U.S. attorney of that." 
 
 The Justice Department's probe of the accident is continuing, it said recently. Its investigation has so far resulted in a criminal indictment against the former head of safety at the Upper Big Branch mine for allegedly attempting to destroy evidence. He has pleaded not guilty. 
 
 The April 2010 explosion at Massey's Upper Big Branch mine in Montcoal, W.Va., was the worst U.S. coal-mining disaster in 40 years. It resulted in several wrongful-death lawsuits against Massey and led to the resignation of the company's chief executive and the sale of Massey to Alpha Natural Resources Inc. of Abingdon, Va. 
 
 At a briefing Wednesday in Beaver, W.Va., Kevin Stricklin, coal administrator for mine safety and health at the Mine Safety and Health Administration, said, "We found there to be two sets of books" kept by Massey. 
 
 "Onshift reports," written by Massey miners, are for recording any hazardous conditions and gas levels at mines. These reports, co-signed by mine management, are shown to government inspectors. The others were "production reports" detailing coal output and any reasons for production delays, including safety issues, also written by Massey employees. MSHA didn't say if the two sets of reports were written by the same workers. 
 
 Mr. Stricklin cited three examples in which onshift reports didn't include hazards noted in production reports. One production report noted hazards such as low air flow that didn't appear in an onshift report shown to government inspectors, he said. 
 
 View Full Image Mine Safety and Health Administration A section of a federal report rebutting the company's finding that traced the origins of the blast to a crack on the mine floor. 
 
 Federal law requires a mine employee to conduct an on-shift examination in each area where miners are working at least once a shift to check for hazardous conditions, test for methane and oxygen and determine if airflow is adequate. All hazards are required to be included in onshift reports for government inspectors. 
 
 Mr. Stricklin said federal investigators concluded that the explosion occurred because broken water sprays on a cutting machine failed to put out an initial spark that ignited methane gas and triggered a coal-dust explosion. He said a gas detector that should have tested for potentially explosive methane hadn't been turned on since March 18, 2010, more than two weeks before the explosion. 
 
 Mr. Stricklin said a crack in the mine's floor that Massey had identified as the source of the inundation of methane was too shallow and not connected to a potential gas source below. Moreover, gas readings before the accident and just after it showed methane levels far lower than would have been expected with an inundation, he said. 
 
 Alpha bought Massey this month for $7.1 billion. Ted Pile, an Alpha spokesman, said, "Alpha is hearing this information from MSHA at the same time everyone else is. Obviously we'll look at this claim [regarding the two sets of records] as well as all information that's available to us as we conduct our own review into what took place at Massey's Upper Big Branch mine in April 2010." 
 
 Mr. Pile said Alpha's review is in its early stages and that the company is starting to assemble specialists. "The full MSHA report, when it's made available, will be part of what our team will closely review," Mr. Pile said. 
 
 Massey completed a 102-page report, which was released by former Chairman Bobby R. Inman after the company was sold, saying the explosion was caused by an inundation of natural gas, a naturally occurring event beyond its control. 
 
 Massey's report said water sprays functioned adequately. This report didn't address book-keeping practices. Mr. Inman couldn't be reached to comment. 
 
 Alpha previously criticized the release of the Massey probe report, calling it unauthorized. 
 
 An independent report released in May by J. Davitt McAteer, the top mine regulator in the Clinton administration, and commissioned by former West Virginia Gov. Joe Manchin while he was in office, found Massey operated the mine in a "profoundly reckless manner" and was largely to blame for an explosion. 
 
 At the time, Massey said it disagreed with Mr. McAteer's conclusion that the explosion was fueled by coal dust, and said, "We believe the explosion was caused by a massive inundation of methane-rich natural gas." 
 
 MSHA and Massey officials have clashed repeatedly since the accident over various reports regarding levels of highly explosive methane gas and combustible coal dust within the mine. Nongovernment safety experts said the government's findings, which put most responsibility for the accident on mine management, could have a bearing on wrongful-death lawsuits stemming from the blast. 
 
 Chris Davis, a Beckley, W.Va., lawyer representing two families who filed wrongful-death lawsuits, said about five such suits have been settled and more than 10 were still pending. 
 
 "This much we already know. The tragedy at the Upper Big Branch mine was preventable," said Labor Secretary Hilda Solis in a brief video presentation Wednesday. 
 
 Write to Kris Maher at kris.maher@wsj.com ||||| America 
 
 Officials: W.Va. Mine Operator Kept Two Sets Of Safety Records 
 
 itoggle caption Jeff Gentner/AP 
 
 Federal mine disaster investigators disclosed a few pieces of new information Tuesday night from their year-long look at the April 2010 deadly Upper Big Branch mine explosion. They said that: 
 
 — Mine owner Massey Energy kept two sets of records that chronicled safety problems. One internal set of production reports detailed those problems and how they delayed coal production. But the other records, which are reviewed by federal mine safety inspectors and required by federal law, failed to mention the same safety hazards. Some of the hazards that were not disclosed are identical to those believed to have contributed to the explosion. 
 
 — Portions of the Upper Big Branch mine hit by the explosion were not treated for excessive and explosive coal dust because the entryways or tunnels in those areas were too small to accommodate the machine used to spray the material that neutralizes coal dust. 
 
 — Gas readings taken shortly after the explosion showed too little methane to support Massey Energy's claim that a massive, naturally-occurring and unpredictable inundation of gas caused the disaster. 
 
 — The path of the fiery blast that accompanied the explosion traveled in more complicated and convoluted ways than reported earlier. 
 
 Those details come from a private briefing in Beckley, W.Va., held last night for the families of the 29 mine workers killed in the disaster. Six participants provided those details to NPR. 
 
 The participants said the Mine Safety and Health Administration (MSHSA) presented findings that support its earlier, preliminary conclusions, as well as those of an independent team of investigators, who issued their final report last month. 
 
 Massey Energy was recently absorbed by Alpha Natural Resources in a friendly takeover. An Alpha spokesman told NPR before last night's private briefing that the company would have no comment on any new information until after a public briefing set for 10 am ET today. 
 
 MSHA told the families that its final report should be ready this Fall.
– The explosion at the Upper Big Branch mine that killed 29 people was caused by safety concerns that owner Massey Energy was well aware of, but hid from federal regulators, according to a new report from the Mine Safety and Health Administration. “This much we already know. The tragedy at the Upper Big Branch mine was preventable,” Labor Secretary Hilda Solis said in a video this morning at a briefing on the findings in West Virginia, according to the Wall Street Journal. Massey actually kept two sets of safety records, the report found—one for federal regulators, and another internal one that detailed all sorts of other problems, some of which are believed to have caused the Upper Big Branch explosion, NPR reports. Other findings include: Massey failed to control the build-up of explosive coal dust, regulators said, and in some places tunnels weren’t even big enough to accommodate the machine that neutralizes such dust There wasn’t enough methane in the mine to support Massey’s claim that an unpredictable, natural surge of gas caused the blast. Faulty water spouts failed to douse the initial spark that started the blast.