The self-styled "BTK" serial killer is now the "prime suspect" in at least two more unsolved killings, leading authorities to conduct another search at the site of his former Kansas home.

Dennis Rader — who nickname himself "BTK" for “bind, torture and kill" — was convicted in 2005 after pleading guilty to killing 10 people between 1974 and 1991 in Wichita and Park City, Kansas.

The Osage County Sheriff's Office in Oklahoma announced in a Wednesday news release that Rader, 78, is the "prime suspect" in the disappearances of a woman and a teenager who both vanished during the time of his killing spree.

The primary focus of a search at Rader's former home in the Kansas suburb of Park City is the 1976 disappearance of Cynthia Kinney, a 16-year-old cheerleader from Pawhuska, Oklahoma, the sheriff's office said. Her body has never been found.

Investigators were also able to connect Rader to the killing of 22-year-old Shawna Beth Garber in McDonald County, Missouri, Osage County Undersheriff Gary Upton told USA TODAY. Garber was found dead in December 1990, having been raped, strangled and restrained.

It wasn't until 2021 that her remains were identified.

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Search uncovers 'items of interest'

Armed with shovels, metal detectors and other tools, investigators led by Osage County Sheriff Eddie Virden combed the land at Rader's former home for "items of evidentiary value based on specific leads," the sheriff's office said in the news release.

Officials in Park City also allowed for city crews to tear up concrete sidewalks poured in the years since Rader has been imprisoned to allow investigators to search underneath, Upton said.

The agency had originally visited the property in April, where Upton said a preliminary dig led investigators to find a pantyhose ligature tied in a knot, which would be consistent with someone being bound at the ankles or wrists.

The sheriff's office said that the more recent search on Tuesday led investigators to find "items of interest," which Upton said appeared to be "personal effects that would belong to a victim." Upton declined to be more specific about what specifically was found during the search.

The sheriff's office said the items would undergo a thorough examination to determine whether they are relevant to the ongoing investigation.

Investigation reopened after sheriff interviews Rader at prison

Cynthia's case was reopened in December after Upton said Sheriff Virden interviewed Rader at the El Dorado Correctional Facility in Kansas.

As Virden was leaving the interview following hours of discussion, Upton said the convicted killer made an unsolicited suggestion that he had once abducted a girl from a laundromat.

The comment prompted the sheriff to further investigate Cynthia's disappearance. She was last seen at a laundromat.

A 1976 entry in one of Rader's journals, obtained by investigators, included the phrase “bad wash day," Upton said. An excerpt of Rader's writings provided to USA TODAY makes mention of a laundromat, which Rader called "a good place to watch victims and dream."

Because Rader was a regional installer for ADT Security Services at the time, Upton said investigators also believe it possible that Rader was installing security footage at a bank being built across the street from the teen's home, making it easier for him to stalk her.

Closure?

As the sheriff's office re-examines whether Rader was responsible for additional missing persons cases and unsolved murders, Upton said Virden remained in Kansas on Thursday to follow up on another investigatory tip. While the sheriff's office said in the release it was working closely with the Kansas Bureau of Investigation, it was unclear just how many other missing person and homicide cases are being re-examined.

Bureau spokeswoman Melissa Underwood confirmed to USA TODAY that the agency has met with the Osage County Sheriff’s Office but that it was not involved in the recent property search.

"Clearly we can't get anything more out of Dennis than what has already been heaped upon him," Upton said. "The bets we can hope for is closure for the families and a sense of understanding of what happened."

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Who was the 'BTK Killer?'

Rader was responsible for at least 10 known slayings that took place across 27 years in the Kansas area. Giving himself the nickname "BTK," Rader would often send notes to police and media outlets with details of his violent crimes.

After seemingly going silent for 13 years, Rader resurfaced in 2004 when he once again began sending the taunting letters, which eventually led to his arrest in 2005.

Rader ultimately confessed to 10 murders and is now serving 10 consecutive life prison terms.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected].