Former Massey Energy chief executive officer Dan Blankenship was indicted on Nov. 13 on federal charges related to the investigation of the 2010 explosion at Upper Big Branch Mine that killed 29 miners.

Blankenship is accused of conspiring to violate safety and health standards at mine. He is the highest-ranking executive to face charges in the blast. The explosion and investigation afterward led to the overhaul of the way the federal government oversees mine safety, ABC News reported.

U.S. Attorney Booth Goodwin said a federal grand jury indicted Blankenship on charges including conspiracy to violate mandatory federal mine safety and health standards, conspiracy to impede federal mine safety officials, making false statements to the Securities and Exchange Commission and securities fraud.

Blankenship could face up to 31 years in prison if convicted.

Blankenship’s 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.”

In February 2013, a former longtime subordinate testified that Blankenship ordered the widespread corporate practice of warning coal miners about surprise federal inspections. The federal Mine Safety and Health Administration (MSHA) 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 mine safety and health standards at Upper Big Branch from January 2008 until April 2010, when the explosion tore through the mine, ABC News reported.

After the explosion, Blankenship made false statements and representations to the SEC concerning Massey Energy’s safety practices before the explosion. He made similar statements in connection with the purchase and sale of Massey Energy stock, the indictment said.

Alpha Natural Resources bought Massey for $7.1 billion in June 2012. Blankenship, who retired ahead of the merger, has denied any wrongdoing.

Four investigations into the Upper Big Branch explosion 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.

Former White Buck Coal Co. President David Hughart testified about Blankenship’s alleged actions as he pleaded guilty to federal conspiracy charges as part of the investigation. Hughart, who never worked at Upper Big Branch, was eventually sentenced to 3 1/2 years in prison for his role.

Former Upper Big Branch superintendent Gary May was sentenced last year to two years 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 in their criminal investigation of the worst U.S. coal mining disaster in 40 years.

May had 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