MILTON, Pa. — Investigators hope tests on a three-ton hunk of concrete will soon solve the 1989 disappearance of a young mother, by determining whether her remains were fed through a wood chipper and then entombed in the basement of a Pennsylvania duplex.

Sunbury Police Chief Tim Miller announced this month that preliminary results showed the concrete contained wood chips, and he’s waiting to see if they also hold the remains of Barbara Elizabeth Miller.

A forensic pathologist is “dissecting the walls, so to speak, piece by piece, hammer-and-chisel type, looking for the smallest of clues,” Miller, no relation to Barbara Miller, said last week. He called it “mere speculation if a wood chipper was or wasn’t used. Obviously the presence of wood chips in a concrete wall is highly suspicious.”

An affidavit used to obtain a search warrant for the Milton home disclosed that investigators believe the woman may have been killed by her ex-boyfriend, a onetime Sunbury policeman named Joseph Walter “Mike” Egan.

Egan “is and has been the lead suspect in this case since 1989,” the chief wrote in the affidavit.

Egan, a Northumberland resident who trims trees for a living, on Friday flatly denied he had anything to do with Barbara Miller’s disappearance.

“They’re way off base,” Egan said, then promised to have his lawyer provide additional comment later in the day. He declined to name his attorney, and no one called back.

The police affidavit said that several people have said that over the years, Egan would talk about driving past his sister’s home in Milton to “visit” his “old lady,” the same building where police seized the massive chunk of concrete currently being examined.

Egan, 69, who in 1988 was paroled after serving six years in state prison for receiving stolen property and other offenses, a crime he committed as a police officer, reported her missing five days after she disappeared, then moved into her home.

The affidavit says Barbara Miller, then 30 years old, had complained to police in the months before she disappeared about Egan, and days before she vanished, told friends she feared for her life.

Her teenage son, Eddie Miller Jr., said she and Egan had a fight on June 30, 1989, the night she disappeared, over her plans to attend a friend’s wedding without him. Eddie Miller also recalled that the morning after the wedding, Egan was driving his mother’s car, and the tires were covered with yellow clay that he thought was related to concrete work.

“Let me tell you something,” Egan said Friday before ending the brief interview. “It was my car, not her car.”

Seventeen years later, a judge declared Barbara Miller dead, but in recent years the Sunbury Daily Item began looking at the case again, and encouraged Tim Miller to investigate after he became police chief last year.