RENO — The DNA of an unknown woman was on a pair of thong underwear found with Brianna Denison's body along with the DNA of the serial rapist who kidnapped and strangled the 19-year-old college student, Reno police said Tuesday.

The black "Pink Panther" panties found with the body on Friday did not belong to Denison, police said.

They are a "critical piece of evidence" that may have been dropped at the scene accidentally or perhaps left behind to "taunt the police," Reno Police Chief Michael Poehlman said.

Denison, a sophomore at Santa Barbara City College in California, was visiting her hometown over winter break when she was abducted Jan. 20 while she slept on a couch in a friend's home near the campus of the University of Nevada, Reno.

The male DNA found on the underwear was from the same man who committed at least two sexually motivated crimes against other young college women in the area over the past four months, Reno police Lt. Robert McDonald said.

Investigators are trying to determine whether the unknown DNA belonged to another woman who may have been assaulted.

The underwear, which appeared to be worn, also may have been stolen in a burglary or perhaps belonged to a woman who had dated someone and later noticed the garment missing, McDonald said.

The Reno Gazette-Journal first reported on its Web site on Tuesday the discovery of the black thong-style underwear with pink hearts and the head of the cartoon character the Pink Panther.

"What is critical to us is there was DNA on these panties, not Brianna's or anyone else in the house," Poehlman said, adding they were too big to fit Denison.

"Our belief is the suspect in this case left these panties there either to taunt the police, to taunt the community, or somehow didn't realize he had them and dropped them in that regard," he told KKOH Radio in Reno.

"They are a critical piece of evidence to us because someone is missing those panties," he said.

McDonald said it's important the woman who owns the underwear come forward because the information she has may lead police to the serial sexual predator who killed Denison.

Meanwhile, the local community has embraced the request of Denison's family to remember her by wearing and hanging royal blue ribbons on trees.

Blue was Denison's favorite color and her mother, Bridgette, is asking people wear blue instead of the traditional black to a public memorial service scheduled for 7 p.m. Saturday at the Reno-Sparks Convention Center.

The event is titled "Live, Love and Unite in Celebration of Brianna Denison."

A number of craft stores, Wal-Marts and scrapbooking shops say they have sold out of the blue fabric some now are calling "Blue Bri," the Gazette-Journal reported. Blue was Denison's favorite color.

"We have had people in here asking for any shade of blue at this point," said Jerry McGuire, an employee at Ben Franklin Crafts store on Plumb Lane.

Several local Wal-Marts sold out of all blue ribbon this weekend.

"A lot of us who work here have teenagers, so we understand what it's like to want to do something," said Lisa Johnson, a store manager at Jo-Ann Fabrics & Crafts, which sold more than 200 rolls of blue ribbon this weekend.

"I think people want to be able to do something, and this is something small they can do," Johnson said.