Illinois State Police confirmed Wednesday that authorities are investigating an anonymous letter claiming a sighting of missing Stacy Peterson.

The letter's author said he or she confronted a woman matching Peterson's description in a Florence, Ky., mall parking lot on Nov. 18. after Peterson was reported missing Oct. 29.

The letter was sent to former Bolingbrook Police Sgt. Drew Peterson, a suspect in his wife's disappearance. Peterson denies any involvement and claims she left him for another man. Peterson has not been charged.

Joel Brodsky, Peterson's attorney, turned the letter over to investigators, said Illinois State Police Trooper Mark Dorencz.

Pam Bosco, a spokeswoman for Stacy’s family, said the letter doesn’t make sense.

“It’s a total waste of time for the Illinois State Police,” Bosco said.

Sgt. Luis Gutierrez, a spokesman for Illinois State Police, said investigators would treat the letter like any other lead. The investigation includes nearly 900 leads, Gutierrez added.

Peterson's attorney said Peterson opened the anonymous letter on Sunday. The author claims seeing the woman with another man in the parking lot of a shopping mall.

The writer of the letter claims to have spoken to Stacy. The letter says Stacy told the writer to "just mind your own business" and "please don't ruin my life."

The writer also claims to have photographed Stacy before she got away.

The investigation continues in the search for Stacy. Authorities recently stopped searching a canal for signs of Stacy but will likely look at other areas when weather improves, Bosco said.

FOXNews.com's Melissa Underwood contributed to this report.