CHARLESTON, W.Va. - Don Blankenship, the steely-eyed executive once dubbed "The Dark Lord of Coal Country," on Thursday became the highest-ranking coal official to face federal charges in the nation's deadliest mine disaster in 40 years.

A federal grand jury indicted the former Massey Energy CEO on numerous counts of conspiracy in the April 2010 underground explosion that killed 29 men at the Upper Big Branch Mine in Montcoal, W.Va.

The 43-page indictment said Blankenship "knew that UBB was committing hundreds of safety-law violations every year and that he had the ability to prevent most of the violations that UBB was committing. Yet he fostered and participated in an understanding that perpetuated UBB's practice of routine safety violations, in order to produce more coal, avoid the costs of following safety laws, and make more money."

His attorney, William W. Taylor III, said in a statement that Blankenship "is entirely innocent of these charges. He will fight them and he will be acquitted."

"Don Blankenship has been a tireless advocate for mine safety," the statement said. "His outspoken criticism of powerful bureaucrats has earned this indictment. He will not yield to their effort to silence him. He will not be intimidated."

But Pam Napper, whose son, Josh Napper, was among the miners who died that day, said "it's about time" Blankenship was called to account.

"He was a big part of this," she said. "He knew what was going on in that mine and continued to let it go. I hope he gets what he deserves. I am so excited. They aren't sad tears today. They're happy tears."

Earlier this year, Blankenship sponsored and appeared in a 50-minute documentary titled "Upper Big Branch - Never Again." In it, he argued that regulators never got to the truth about what happened underground.

"If someone wants to know the truth about what happened at UBB, they need to go ubbneveragain.com and watch the documentary," Blankenship, in his signature even baritone, told MSNBC's Chris Hayes early last month.

But U.S. Attorney Booth Goodwin said the truth is contained in the indictment.

In February 2013, a former longtime subordinate, David Hughart, testified that Blankenship ordered the widespread corporate practice of warning coal miners about surprise federal inspections. The federal Mine Safety and Health Administration said the root cause of the blast was Massey's "systematic, intentional and aggressive efforts" to conceal life-threatening problems. MSHA said managers even maintained two sets of pre-shift inspection books - an accurate one for themselves, and a sanitized one for regulators.

The indictment says Blankenship conspired to violate standards at the mine from January 2008 until April 2010, when the explosion tore through the tunnels.

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The explosion prompted federal officials to begin monthly "impact" inspections at problem mines throughout Appalachia in addition to routine state and federal visits. MSHA said last month that it has conducted 823 "impact" inspections sites and issued more than 13,000 citations since the explosion.

Alpha Natural Resources bought Massey for $7.1 billion in June 2012. Blankenship retired ahead of the merger.

"We can only hope that the outcome of the upcoming proceedings that were announced today will provide some level of comfort and closure for the families of the fallen miners and to the larger community where we live and operate," Alpha said in a statement.

Four investigations into the disaster found that worn and broken cutting equipment created a spark that ignited accumulations of coal dust and methane gas. Broken and clogged water sprayers allowed what should have been a minor flare-up to become an inferno.

Blankenship started a blog to push his assertion that the presence of natural gas in the mine, and not methane gas and excess coal dust, was at the root of the explosion. He said getting to that "truth" was "the best way to honor the victims of Upper Big Branch ..."

In the November 2010 Rolling Stone article in which the "dark lord" moniker was coined, Jeff Goodell described the former $18 million-a-year man as "the undisputed king of coal in West Virginia."

"Other Big Coal CEOs who operate in Appalachia are business-school types who have offices in other states and leave the dirty work to their minions," he wrote. "Blankenship, by contrast, is a rich hillbilly who believes that God put coal in the ground so that he could mine it, and anyone - or any law - that stands in his way needs to be beaten down, bought off or tied up in court.

"Blankenship is hated, feared and respected, but nobody wants to tangle with him."

Until now. If convicted, Blankenship could face up to 31 years in prison.

Others have been convicted in the case. Former White Buck Coal Co. President Hughart, who testified that Blankenship ordered the inspection warnings, pleaded guilty to federal conspiracy charges. Hughart, who never worked at Upper Big Branch, was eventually sentenced to 3 1/2 years in prison for his role.

Former UBB superintendent Gary May was sentenced last year to one year and nine months in prison on charges he defrauded the government through his actions at the mine, including disabling a methane gas monitor and falsifying records. May cooperated with prosecutors.

He testified at the February 2012 sentencing of former Massey security chief Hughie Elbert Stover, who was sent to prison for three years for lying to investigators and ordering a subordinate to destroy documents. It was one of the stiffest punishments ever handed down in a mine safety case.