CHARLESTON, W.Va. (AP) — Former coal executive Don Blankenship jumped back on Twitter on Wednesday, renewing his feud with U.S. Sen. Joe Manchin on the day Blankenship was to finish a one-year prison sentence arising from the deadliest U.S. mine explosion in decades.

Even before the U.S. Bureau of Prisons listed Blankenship as leaving a halfway house in Arizona, the ex-Massey Energy CEO rattled off a series of tweets. He took swipes at a federal mine safety agency and Manchin, the senator from West Virginia where the Upper Big Branch mine exploded in 2010. Blankenship also re-offered his version of what happened at the mine.

"I challenge Sen. Manchin to debate UBB truth," Blankenship wrote, referring to the mine with initials. "A U.S. Senator who says I have 'blood on my hands' should be man enough to face me in public."

Blankenship was referring to an April 2014 statement from Manchin, six months before federal prosecutors announced an indictment against the mine executive.

A Bureau of Prisons spokesman didn't return requests for comment, and Blankenship was still listed late Wednesday afternoon as being at the halfway house. Blankenship still must serve one year of supervised release.

Manchin said in a statement that he hopes Blankenship "chooses to do the right thing and disappear from the public eye."

Blankenship was sentenced last year for a misdemeanor conviction of conspiring to violate federal mine safety standards at Upper Big Branch, where 29 workers died. He was acquitted of felonies that could have stretched his sentence to 30 years.

"I'm glad he had time to reflect on the pain he caused," former U.S. Attorney Booth Goodwin, whose office in Charleston prosecuted the case, said in a text message to The Associated Press ahead of Blankenship's release. "I hope he used it wisely and will come out of prison ready to make amends."

It wasn't immediately clear where Blankenship will serve his supervised release. After his indictment, federal prosecutors indicated Blankenship owned homes in several states, and Blankenship said he lived in Las Vegas. A spokesman for the U.S. attorney's office in Charleston referred questions to the Bureau of Prisons.

Blankenship's attorney, William Taylor, didn't return requests for comment.

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

"He didn't get what he deserved," Davis said.

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

Blankenship has said natural gas, and not methane gas and excess coal dust, was at the root of the explosion. Authorities dismissed that argument.

Massey was later bought by Alpha Natural Resources of Bristol, Virginia. Alpha agreed in 2011 to pay $210 million to compensate the grieving families, bankroll cutting-edge safety improvements and pay for years of violations by Massey Energy. Alpha announced in 2012 that the mine would be permanently sealed.

Blankenship, 67, served most of his sentence at Correctional Institute Taft near Bakersfield, California. While there, he wrote a 67-page blog before his appeal was heard in which he called himself an "American political prisoner."

During the trial, prosecutors called Blankenship a bullish micromanager who meddled in the smallest details of Upper Big Branch. They said Massey's safety programs were just a facade — never backed by more money to hire additional miners or take more time on safety tasks.