Check for updates in our Coal Tattoo blog:MONTCOAL, W.Va. -- Rescuers continued on Tuesday evening with what they admitted is a long-shot effort to save four Massey Energy miners still unaccounted for after a huge explosion that killed 25 workers, injured two others, and brought more calls for safety reforms in the nation's mining industry.State and federal regulators and elected officials promised thorough investigations, even as they struggled to maintain a small slice of optimism following the worst U.S. coal-mining disaster in a quarter century."We've all thrown everything at this rescue effort," said Joe Main, assistant labor secretary for the federal Mine Safety and Health Administration. "We're going to throw the same effort at getting to the bottom of what happened."At a 5 p.m. briefing, Massey vice president Chris Adkins said drilling crews could get ventilation boreholes into his company's Upper Big Branch Mine in Raleigh County by noon or 2 p.m. Wednesday. No significant news on the drilling progress was expected until 8 a.m. Wednesday, officials said.Rescue efforts were abruptly halted early Tuesday morning, when officials detected dangerous levels of methane that presented a risk of another explosion that would endanger rescue teams.Kevin Stricklin, MSHA's administrator for coal mine safety, said the massive explosion damaged many of the ventilation walls that control the flow of fresh air and keep down methane levels. Stricklin said ventilation fans appear to be working, but aren't providing enough airflow to reduce methane to safe concentrations.Adkins said he's 90 percent certain where the four remaining missing miners are, and once rescuers can get into the mine, teams should be able to reach them in four or five hours."They should be able to blow the mine out pretty well and get the gases under control and then they should be able to advance pretty rapidly," said Joe Pavlovich, a former MSHA official and mine rescue expert.Gov. Joe Manchin said officials are holding out hope that the four unaccounted-for miners were able to reach an airtight underground rescue chamber with food, water and air that could last them four days or more."Everybody is going to cling to the hope of a miracle," Manchin told reporters, while acknowledging that "the odds are against us."The explosion is believed to have occurred at about 3 p.m. Monday inside the Upper Big Branch Mine, a huge longwall operation that produced 1.2 million tons of coal last year with about 200 workers. The blast occurred near the time for a shift change and some workers were believed to have been on their way out at the time.Manchin said rescue teams described seeing massive damage underground, including mine car rails that were bent "like pretzels," and others said miners thousands of feet away were killed by the strength of the blast.Tim Bailey, a Charleston lawyer who represents miners and their families in safety cases, said such damage indicates an initial methane explosion that was made far more powerful by coal dust that had not been properly cleaned out of the mine."You get the initial explosion, and it just feeds itself out through the mine," Bailey said.The Upper Big Branch is considered a "gassy mine," meaning it generates large amounts of methane. Under a provision of federal law, the operation undergoes more frequent inspections, and those inspections have turned up various violations of mine ventilation standards.In an interview with West Virginia MetroNews, Massey CEO Don Blankenship denied any violations by his company led to the disaster. "Any suspicion that the mine was improperly operated or illegally operated or anything like that would be unfounded," Blankenship said.But MSHA's Stricklin said that's simply impossible."We know it wasn't operating safely, or we wouldn't have had an explosion," Stricklin said."It's quite evident that something went very wrong here," he said. "All explosions are preventable. It's just making sure you have things in place to keep one from occurring."Asked if he was concerned about Massey's safety record, Manchin replied, "I'm not comfortable when there is an accident, no matter who it is."Manchin promised the state would hold a public hearing as part of his investigation, and that he planned to ask Clinton administration MSHA chief Davitt McAteer to help the state work out the details of its probe.Rep. Nick J. Rahall, D-W.Va., said that House Labor Committee Chairman George Miller, D-W.Va., had committed to holding hearings to investigate the disaster.In a prepared statement, Labor Secretary Hilda Solis said, "Twenty-five hardworking men died needlessly in a mine yesterday. I pledge that their deaths will not be in vain. Miners should never have to sacrifice their lives for their livelihood."The explosion was the worst U.S. mining disaster since December 1984, when 27 workers died in a fire at the Wilberg Mine in Orangeville, Utah. It was the worst disaster in West Virginia since 78 miners -- including Manchin's uncle -- died in the November 1968 Farmington Disaster in Marion County."Clearly, we must get to the bottom of what happened, how and who was responsible," said Sen. Robert C. Byrd, D-W.Va. "And we must and will hold those parties accountable."West Virginia's coal miners are the backbone of a great nation that depends on their work," Byrd added. "They deserve nothing less than a safe working environment, and an employer who respects and values their safety."Tuesday afternoon, the state Medical Examiner identified the first seven victims of the disaster: Steven J. Harrah, 40; William R. Lynch, 59; Jason Atkins, 25; Benny Ray Willingham, 61; Carl Accord, 52; Deward Allan Scott, 58; and Robert E. Clark, 41.Other names were not officially released, but identities of the dead and missing began to spread as national and international media descended on the Raleigh County area to cover the story.Some family members were vocally critical of Massey, saying the company did not contact them or provide adequate information and support in the hours after the explosion."We sat and we sat and we sat," said Michelle McKinney, whose father Benny Willingham was among those killed. "We are still waiting on that phone call."Reach Ken Ward Jr. at email@example.com or 304-348-1702.Reach Gary Harki at firstname.lastname@example.org or 304-348-5163.Reach Andrew Clevenger at email@example.com or 304-348-1723.