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Oklahoma investigators were in Kansas on Tuesday, as officials say they are investigating missing persons and murder cases which might be tied to serial killer Dennis Rader, who's also known as BTK for his preference to "bind, torture and kill," his victims.

Rader confessed to killing 10 people after being arrested in 2005. Investigators were back at Rader's former Park City, Kansas, property Tuesday to follow-up on leads of murders and missing people which may be tied to Rader.

"Osage County Sheriffs Office is continuing to follow leads in unsolved missing persons and murder cases possibly related to BTK. The investigation is ongoing at this time, and I still have investigators out in the field so I can’t comment any further," Undersheriff Gary Upton said.

Park City police and the Kansas Bureau of Investigation was also present as investigators searched Rader's former property, which is now city-owned property.

SERIAL KILLER BTK SAYS PRISON CELL SEARCHED AMID COLD-CASE PROBES; DENIES INVOLVEMENT

Dennis Rader frowns in court

Serial killer Dennis Rader stands before Sedgwick County District Court Judge Greg Waller as sentencing is read Aug. 18, 2005, in Wichita, Kan. Rader received nine life terms and a "hard 40" for the 10 murders he committed over nearly 30 years ago. (Bo Rader-Pool/Getty Images, File)

Upton said the search spiraled from the investigation into Cynthia "Cyndi" Dawn Kinney, a 16-year-old cheerleader who was last seen leaving a relative's laundromat on June 23, 1976.

Fox News Digital previously reported that prison guards seized Rader's belongings during a meeting with cold-case investigators.

Kerri Rawson, Rader's daughter, told Fox News Digital on Tuesday that "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."

SERIAL KILLER BTK LAYS OUT ALIBI AMID NEW QUESTIONING OVER 1976 OKLAHOMA COLD CASE

FILE - In this Oct. 12, 2005, file photo, convicted BTK killer Dennis Rader listens during a court proceeding in El Dorado, Kan. A new book says the BTK serial killer planned to kill an 11th victim by hanging her upside down in her Wichita, Kansas, home. It’s a story police heard from Dennis Rader himself in 2005, but decided at the time to suppress to protect the woman. The story was made public in

Convicted BTK killer Dennis Rader listens during a 2005 court proceeding in El Dorado, Kan. (Associated Press, File)

She said investigators dug a hole where the shed used to be.

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Dennis Rader mugshot

BTK murder suspect Dennis Rader stands for a mug shot released Feb. 27, 2005, by the Sedgwick County Sheriff's Office in Kansas. (Getty Images, File)

Rader has previously denied involvement in the cold case and said he was "done" speaking with Osage County Sheriff Eddie Virden, but said he "enjoyed" meeting with investigators regarding the disappearance of Shawna Garber, who went missing on Halloween in 1990.