NASHVILLE, Tenn. — After finishing a one-year prison sentence, a former West Virginia coal executive has wasted no time resuming a campaign for vindication in the deadliest U.S. mine disaster in four decades.

In a phone interview Friday, ex-Massey Energy CEO Don Blankenship took up the same fight he waged before his 2015 trial: to convince people that natural gas, and not methane gas and excess coal dust, was at the root of the explosion at Upper Big Branch Mine in West Virginia, which killed 29 miners in 2010.

Blankenship was sentenced last year for a misdemeanor conspiracy to violate federal mine safety standards at Upper Big Branch. He was acquitted of felonies that could have stretched his sentence to 30 years. He finished his prison term on May 10.

“I know who I am and what I am,” Blankenship said. “And I’m more than 100 percent innocent, and the charges were ridiculous. And all the emotion and all the publicity about it was just incorrect, which has been the case with me for years and years.”

Authorities have long dismissed Blankenship’s argument, and have shown no signs of changing that. U.S. Sen. Joe Manchin, a longtime rival, said he hoped Blankenship would “disappear from the public eye” after his release from prison.

Among his many criticisms of the trial and prosecution, Blankenship took issue with family members of deceased miners being allowed in the courtroom, while testimony on the explosion itself was barred because he wasn’t charged with causing the explosion. And it was unfortunate, he said, that the judge wouldn’t let him or the parties bring up the explosion.

“It was sort of irreconcilable that we were packed with family members whose loved ones had been lost, as if it was something I had caused,” Blankenship said. “But yet, the trial, as ordered by the judge, and the jury was instructed, had nothing to do with the explosion.”

At Upper Big Branch, four investigations found worn and broken cutting equipment created a spark that ignited accumulations of coal dust and methane gas. Broken and clogged water sprayers then allowed what should have been a minor flare-up to become an inferno.

On his release date, Blankenship immediately tweeted up a storm, saying federal mine regulators had lied. He later wrote a letter to President Donald Trump that he should re-examine the Upper Big Branch investigation, and quickly challenged Manchin to debate what happened in the deadly mine blast.

A federal appeals court upheld Blankenship’s conviction in January. He has said he will appeal to the U.S. Supreme Court.

Manchin’s spokesman, Jonathan Kott, has since said that out of respect for the families, the Democratic senator “is not going to comment about this anymore.”

Blankenship, 67, now lives in Las Vegas and has the resources, despite the case, to comfortably retire, though he may pursue other opportunities, he said.

While in prison, options to pass the time were limited, he said: sleep, eat, socialize, play card games or chess, watch television, exercise, check email on a limited basis and take up to 10 minutes a day allotted for phone calls. His main duty in prison was cleaning and housekeeping. He also had time to write up a small booklet named “An American Political Prisoner,” another effort to clear his name.

Former Upper Big Branch miner Tommy Davis, who lost a son, brother and a nephew in the explosion, has said Blankenship should still be in prison.

“He didn’t get what he deserved,” Davis said.