Authorities recently conducted a search of BTK Killer Dennis Rader’s former Park City, Oklahoma property in the hopes of finding evidence linking the serial killer to additional murders.

“The Osage County Sheriff’s Office is continuing to follow leads in unsolved missing persons and murder cases possibly related to BTK,” Osage County Undersheriff Gary Upton said in a statement to CNN Tuesday. 

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Undersheriff Upton additionally told ABC affiliate KAKE that investigators were motivated to dig on the property after receiving a tip in connection to the 1976 disappearance of 16-year-old Cynthia “Cyndi” Kinney. He added that they are following “all leads, some of which are very interesting.”

Kinney went missing after leaving her job at an Osage, Oklahoma laundromat owned by her aunt and uncle on the morning of June 23, 1976. Initial reports suggested that she was picked up by two women driving a Plymouth, according to the Charley Project, which highlights missing persons cold cases.

Rader’s daughter Kerri Rawson told Fox News Tuesday that investigators are specifically interested in trophies from potential victims that Rader may have hidden. “The theory is he could have placed evidence of cases under stone pavers under the metal shed he built early to mid 90s. Like drivers licenses in jars,” she explained.

Rader, who is currently serving 10 life sentences for murders that took place in Kansas between 1974 and 1991, has twice been questioned by police in connection to the Kinney case but he told Fox News in April that he had no involvement in Kinney’s disappearance. “The sheriff has what I call complete lack of solid evidence,” Rader said.

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The serial killer said that he is being eyed as a potential suspect since he had previously worked for ADT, which did security for a bank across the street from the laundromat where Kinney was last seen. However, Rader claimed that he wasn’t in the area at the time of Kinney’s disappearance and he didn’t move to Oklahoma until 1990. 

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“Give me a break. I drove down there on a whim to Osage County, from Wichita, when I’d never been there before,” he said. “I helped on 1990 Census in Oklahoma, but the timeframe doesn’t match anything I did.”

Rawson told Fox News that she’s inclined to believe her father considering he’s been forthcoming about his crimes since his 2005 arrest. Additionally, she noted that Rader typically stalked and broke into his victim’s homes prior to murdering them, neither of which seemed to occur in the Kinney case.

“While it is my hope and prayer this missing person cold case gets solved for the family and friends of Kinney, in no way do I believe my father is connected. And, in fact, I believe he’s telling the truth on this, as he has done since 2005 on the 10 he did commit,” Rawson explained.

In the aughts, Rader taunted police through a series of letters, which led to his capture in 2005. Once arrested, police said that Rader confessed to murdering 10 people, starting in the ’70s, and would not “shut up” about his crimes.