(CNN) -- A cryptic confession on the popular PostSecret blog had Chicago police searching a city park over the weekend for a possible homicide victim.
The anonymous message appeared as one of the Sunday Secrets posted weekly on the PostSecret blog. Followers of the blog mail postcards illustrating their anonymous secrets to website founder Frank Warren. Each Sunday, Warren scans a selection from the thousands mailed to him and uploads them to the blog.
The postcard in question appeared as the top image Sunday and showed what appeared to be an aerial map of a park. A Post-It style note attached to the image read, "I said she dumped me, but really I dumped her (body)," with a red arrow pointing to a particular spot.
Eagle-eyed users of the website Reddit helped identify the exact location on the postcard as Chicago's Jackson Park, and the post quickly spread across social media. It also caught the attention of the Chicago Police.
"We basically had a cryptic message observed on the site pertaining to a possible criminal act," Officer John Mirabelli told CNN Monday. "Officers immediately went to the park and conducted a search. There was no evidence of a crime or anything that was unusual."
Police detectives will continue to investigate, "but nothing has surfaced to indicate that a crime was committed," Mirabelli said.
Reaction to the posting varied. On its Twitter page, PostSecret retweeted comments, including one from Paige Bernard, who wrote, "thank you for posting that really chilling confession. Even the scariest secrets need to be heard."
Another user expressed outrage: "posting that photo and map of a where a dead woman's body may lay, is exploitative and wrong. What is wrong with you!?!"
While it appears the postcard was a hoax, authorities are not finished with their investigation.
"If the intent behind the message was to cause alarm and cause the police to search that location, then it is a crime -- like screaming fire in a crowded theater," Mirabelli said. "But it depends on the offender -- are we dealing with a child or an adult? A whole lot of factors to consider."
The postcard implying that a killing may have been committed remained at the top of the website Monday. Warren did not return a CNN request Monday for comment.
Warren started PostSecret as an art installation in 2004, handing out self-addressed postcards inviting people to share their secrets with him anonymously. The idea went viral, with Warren receiving more than a half-million postcards in nearly 10 years -- all sent to his Germantown, Maryland, home. Secrets range from the funny ("I walk across campus so I can poop in the dorm with the nice bathrooms," one secret posted Sunday reads) to the downright eerie ("Everyone who knew me before 9/11 believes I'm dead," is one Warren shares regularly when he gives talks on the website on college campuses).