SEATTLE, Wash. -- Colorful origami butterflies found around Seattle displaying ominous messages appear to be connected to an anti-abortion campaign.

The folded papers, which were found this week in Capitol Hill, the U-District, South Lake Union and downtown, generated a lot of chatter on social media.

The folded papers have a puzzling warning about safety, but no one seems to know who is behind the campaign or what it’s about.

When unfolded, the message “you are not safe,” is revealed and there is a date: 9-28-17. The flip side has illustrations of Russell Wilson, Kurt Cobain, the Starbucks siren, and a message about peace.

“It could be a marketing gimmick for an artist or something, I don't know,” said Henry Bridges, who found one of the papers in Capitol Hill.Some Facebook users thought the messages were some sort of marketing effort for an Insane Clown Posse concert scheduled in Seattle for Thursday. Others said the messages were tied to a band in Michigan. Some tried to look into the website's source code to see who was hosting the site.

“I had some friends at Amazon say they're not going to go to work on the 28th, so, Amazon, if people aren't showing up on the 28th, now you know why,” Marc Shelffo, who also kept one of the papers, which he thinks started showing up this week.A website listed on some of the papers directs people to the same “you are not safe” message, along with the 9-28 date.Seattle police said on Wednesday afternoon that they did not believe there were any safety concerns related to the origami, which they thought might be part of an ad campaign of some sort.A campaign called The Tenth Mark appears to be behind the messages. Its site displays the same images and YouTube videos conveying anti-abortion and religious sentiments.“Do not be alarmed. We mean you no harm. But we have come to invade your safe space,” the site reads.Links on the website for more information are directed to a group called Abolish Human Abortion.The site domain is registered through a service that protects the owner's identity.The website doesn’t address the date printed on the origami butterflies, but September 28 is recognized by some groups as a "global day of action for access to safe and legal abortion."