ERIE, Pa. — A man claiming to be the common-law husband of a woman convicted in a bizarre bank robbery plot that killed a pizza delivery driver with a bomb locked to his neck wants federal prison officials to confirm her death and to release her remains.

The Bureau of Prisons has said 68-year-old Marjorie Diehl-Armstrong died April 4 of natural causes at the Federal Medical Center-Carswell, a 1,400-inmate medical facility for females in Fort Worth, Texas.

Diehl-Armstrong was serving life plus 30 years in the 2003 Erie bank robbery plot that ended with the death of 46-year-old pizza deliveryman Brian Wells. Wells had been forced to rob a bank while wearing the metal collar bomb that exploded afterward as he sat, handcuffed, in a parking lot while police and the FBI waited for a bomb squad.

Mark Marvin, of Walden, New York, told the Erie Times-News on Monday that the U.S. Bureau of Prisons hasn’t cooperated with helping him locate Diehl-Armstrong’s remains or even confirming to his satisfaction that she’s dead.

“It is certainly reasonable to believe she died,” Marvin said. “But I don’t have any confirmation of that.”

If she is dead, he wants to move her remains to a Quaker cemetery near Poughkeepsie, New York.

“I am just pursuing her interests,” Marvin told the newspaper. “She insisted she is not guilty.”

Marvin said he met Diehl-Armstrong by mail while he was corresponding with her fellow inmates and helping them with legal issues, though he’s not an attorney.

A Bureau of Prisons spokesman said Tuesday the bureau doesn’t comment on matters related to legal proceedings.

The U.S. attorney’s office in Pittsburgh, which oversees the satellite office in Erie where Diehl-Armstrong was convicted, also declined to comment. The office must file a response to Marvin’s petition.

Wells’ death remained a mystery until Diehl-Armstrong and her fishing buddy Kenneth Barnes were indicted in 2007 on charges they concocted the plot along with her ex-boyfriend William Rothstein, who by then had died of cancer.

Barnes later pleaded guilty and testified against Diehl-Armstrong. Federal prosecutors said Rothstein, a retired high school shop teacher, made the collar bomb using two egg timers provided by Diehl-Armstrong. They said he ordered the pizzas that lured Wells to a dead-end road, where Wells was fitted with the device and given handwritten instructions on how to rob the bank and disarm the bomb.

Prosecutors contend Wells was in on the plot but was fooled into believing the collar bomb would be a decoy. His family disputes that and maintains he was a hostage.