PAWHUSKA, OSAGE COUNTY: Dennis Rader, the notorious BTK serial killer who confessed to murdering 10 people in Kansas, may have left behind more clues and victims than he admitted.

Investigators in three states are digging into his past and searching for evidence in two cold cases that could be connected to him. BTK is currently serving 10 consecutive life sentences in a Kansas prison.

What did investigators find in Rader’s journals?

One of the cases is the disappearance of Cynthia “Cyndi” Dawn Kinney, a 16-year-old cheerleader who vanished from a laundromat in Pawhuska, Oklahoma, in 1976.

On that day, Rader’s former employer, the ADT security firm, worked across the street at a new bank.

Osage County Sheriff Eddie Virden says his team found a passage in Rader’s journals that seems to refer to Kinney’s case: “Bad Wash Day.”

“Laundry Mat were a good place to watch victims and dream,” the passage reads. “Sometime I have a pair of women underwear on and after watching a girl or lady, retrieve (sic) myself in bathroom…”

What did investigators find on Rader’s property?

“We located several items that we believe are related to crimes or possible victims from Dennis Rader,” Virden told Fox News.

They also broke through concrete and found more “items of interest” that the sheriff says are evidence of Rader’s crimes.

Virden also says they recovered knotted pantyhose and other “items of interest” from Rader’s former property in Park City, Kansas.

What is the other cold case that Rader is a prime suspect in?

Another cold case that has caught investigators’ attention is the murder of Shawna Garber, a 53-year-old Kansas woman who was last seen on Halloween in 1990.

Her case is being handled by the McDonald County Sheriff’s Office in Missouri. Garber was raped, strangled, and hogtied in Radar's signature style, which he used to kill other victims.

Her remains were found on property across the Missouri state line, still bound. Virden considers Rader a prime suspect in both cases and visited him in prison with other investigators in April.

He says they are also looking into Rader as a possible suspect in other cases, but declined to give specifics.

How did Rader react to the investigations?

Rader, now 79, was arrested in 2005 after years of playing cat-and-mouse games with investigators and the media.

He gave code names to his victims, calling them “projects,” wrote detailed notes, and kept trophies from his kills. He also has code names that investigators have not yet cracked: among them, “Prairie,” “Iron Mountain,” and “Bad Wash Day.”

Rader has denied involvement in any killings other than the 10 murders he already pleaded guilty to. He says he wasn’t involved in work at the bank in Pawhuska and called the Kinney investigation “a BTK witch hunt.”

Rader told Fox News that detectives and “Feds” have visited several other locations as well, including his father’s property in Missouri, “looking for dead bodies [and] clues elsewhere.”