Investigators say they are searching the former Park City, Kansas, property of Dennis Rader, the self-proclaimed "BTK Killer" who pleaded guilty to murdering 10 people between the 1970s and 1990s.

"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 told CNN Tuesday. He declined to comment further, citing the ongoing investigation.

Rader, who is serving 10 consecutive life terms in prison, admitted in 2005 to carrying out the brutal killings to fulfill his sexual fantasies. He suggested in a letter found long before his capture that he should be called "BTK," short for "bind, torture, kill."

Park City police were also on site Tuesday as authorities searched the site of Rader's former home in the Wichita suburb, Upton said.

Rader, now 78, admitted to the string of murders in the Wichita area from 1974 to 1991. The dedicated churchgoer and married father of two described in court how he chose and stalked his victims before killing them. In more than one case, the killer said he took Polaroid photos of his victims.

Among his victims were two women who worked with him in an office as well as a co-worker's husband and two children.

As Rader went uncaught for decades, he continued mailing cryptic letters to the media and investigators -- a practice that ultimately lead to his capture. Rader was arrested in 2005 after police traced a floppy disk he mailed to a local TV station to a computer at his church. Investigators then determined that Rader's DNA matched the killer's.

Rader is incarcerated at the El Dorado Correctional Facility in Kansas.