It was back on April 5, right around the afternoon shift change, when methane gas or coal dust or both suddenly ignited in the Upper Big Branch coal mine in West Virginia, sending a massive fireball shooting down its low-ceilinged passageways.
Twenty-nine miners working in several different sections of the mine were killed instantly, making it the deadliest mining disaster in 40 years.
The conflagration was so intense that federal officials investigating its cause had to wait two months before the risk of fire and the levels of methane in the air were low enough that they could start looking for clues underground.
Today, Upper Big Branch remains closed to everyone but those investigators, who are still only partway through their methodical examination.
Federal Mine Safety and Health Administration director Joseph A. Main went down into the mine a few weeks ago and all around him, he said, were signs of "a pretty violent explosion."
"You have ventilation controls that are destroyed -- your block walls are blown out -- you have residue from the heat and fire," he said in an interview with the Huffington Post. The floors are littered with debris and damaged equipment. There was, Main said, "a vast area that was affected."
MSHA's operating theory appears to be that something Massey did to the mine's ventilation system let methane and possibly dust build up to explosive levels.
Before the explosion, Upper Big Branch had received more "unwarrantable failure" orders -- for safety violations that constitute more than just ordinary negligence -- than any other mine in the country, Main said.
Civil and criminal investigations are both underway.
And federal officials have now disclosed that they found handheld methane monitors deep inside the mine that had maxed out, suggesting explosive quantities of the gas.
"Without a doubt, something went wrong with the ventilation," Main said. "Ventilation is used to render harmless methane in a mine. And that didn't happen."
Meanwhile, as generally happens in response to a major accident, the regulatory environment is changing.
After the explosion, MSHA was hammered for letting mines with alarming safety records exploit loopholes to evade fines and stay open. A June memo from the Department of Labor's Inspector General found that between 2007 and 2009, MSHA apparently declined to subject some problem mines to closer scrutiny because it was too much work.
Since the April explosion, Main has dramatically stepped up MSHA's enforcement activities.
A reform bill making its way through Congress would expand the mine regulator's authority, but what's already changed is that inspectors are now using preexisting powers to a much fuller extent -- particularly their ability to conduct surprise inspections and pull workers out of mines with serious health hazards until those hazards have been abated.
"We're aggressively using the closure order as a tool of choice" Main said.
"I see more withdraw orders than I ever saw in the past," said Ellen Smith, the managing editor of Mine Safety and Health News. "MSHA's always had power to issue them," she said, "they just didn't use the power that they had to the fullest extent. They're doing that now. They've never done it before, under anyone."
MSHA statistics show 1,287 closure orders between April 5 and August 5 of this year, 285 more than during the same period last year.
Smith said she's even heard of surprise inspections in off hours. "For MSHA to go into a mine on third shift was unheard of," she said.
As the Associated Press reported Thursday, MSHA is cracking down on mine companies that tip off their underground workers before federal officials making surprise inspections can get down there themselves.
And although the money hasn't arrived yet, Congress recently appropriated $18.2 million for MSHA to prosecute appeals of its citations, and $3.8 million to the Federal Mine Safety and Health Review Commission to help reduce a massive backlog of cases.
On the Hill, legislation introduced by Rep. George Miller (D-Calif.) has passed by the House Judiciary Committee but not the full House; Sen. Jay Rockefeller (D-W.Va.) has introduced nearly identical legislation in the Senate. The bills would give MSHA more leverage over mine operators with troubling safety records and would further protect workers who speak up about safety concerns.
Meanwhile, the mammoth Massey Energy Company and its famously combative CEO, Don Blankenship, remain entirely unapologetic.
Late last month, Blankenship lectured a Washington crowd about morals and said that accidents happen. "I believe that the physics of natural law and God trump whatever man tries to do," he said. "Whether you get earthquakes underground, whether you get broken floors, whether you get gas inundations, whether you get roof falls, oftentimes they are unavoidable just as other accidents are in society."
That same day, his company officially tried to shift blame for the accident to a natural event -- a crack in the mine floor that ostensibly created an unusually big and sudden burst of methane.
Blankenship has also publicly urged the families of the victims to settle with the company without hiring lawyers or filing lawsuits. And just this week, he got his way with four of the families, who agreed to settle for undisclosed terms. Massey had previously offered families settlements of at least $3 million each.
One of the most far-reaching changes to the mining industry since the April explosion may actually end up being the insertion -- at the request of Rockefeller and his fellow West Virginia Democrat, the late Sen. Robert Byrd -- of an amendment to the recently passed financial reform bill.
The amendment, now law, requires publicly-traded mining companies to include serious mine safety violations in their public filings with the Securities and Exchange Commission.
Unlike the citations themselves, these SEC filings are closely tracked by shareholders and industry analysts. Indeed, on August 23, Massey filed a notice with the SEC acknowledging that MSHA had, in an enforcement order issued on July 21, accused it of creating an "imminent danger" of death or serious physical injuries.
As it turns out, MSHA investigators working their way through the Upper Big Branch mine had discovered a two-by-two-by-three-foot box labeled "explosives" in a conveyor belt tunnel. The explosives had nothing to do with the April 5 explosion, but nevertheless, this was a big deal.
And because it was in an SEC filing, the market noticed.
Massey Energy stock prices dropped suddenly, eventually falling $4.13, or 13 percent, over the next four days.
Similarly, the first 10-Q quarterly reports were filed under the new law earlier this month, allowing stock analysts like SNL Financial to easily compare and contrast various companies' safety performance. SNL concluded:
Massey Energy Co. racked up, by a wide margin, the highest number of mine safety transgressions among U.S. public coal producers during the second quarter, according to data provided by the companies in their latest Form 10-Q filings.
The U.S. Mine Safety and Health Administration assessed more than $4 million in proposed fines against Massey during the second quarter, a number that far and away exceeded the performance of other public U.S. coal companies. In fact, no other coal producer reporting safety data to the SEC was fined more than $1 million during the second quarter.
"This information is really going to play a huge role in corporate responsibility," Smith said.
Meanwhile, what Main called "enhanced enforcement" continues. "We're finding some pretty egregious things," he said, noting that one mine -- Wilcoal Mining Inc.'s Tri-State One Mine in Claiborne County, Tenn. -- stayed closed for three weeks while it fixed a series of ventilation-related violations, among others.
Main, a former United Mine Workers of America safety official, had already been running MSHA for six months when the Upper Big Branch mine exploded. Some of the changes MSHA has made since the explosion were already in the works before that, he said.
But would a more concerted crackdown before April have saved the lives of 29 miners?
"I think anyone always looks back to figure out what went wrong. What did you miss? What did you miss? Those are things I'll think about for the rest of my life," Main said.
"But the other thing is: you find it and fix it. You learn the lessons of the event and you plan the reforms pretty quick."
Dan Froomkin is senior Washington correspondent for the Huffington Post. You can send him an e-mail, bookmark his page; subscribe to his RSS feed, follow him on Twitter, friend him on Facebook, and/or become a fan and get e-mail alerts when he writes.