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Facebook pages of local police departments, celebrities like Kim Kardashian, and even email blasts from principals to concerned parents across the U.S. warned of a viral meme that claimed children viewing an image called “Momo” while browsing YouTube could result in suicide or self-harm.

The character, according to some rumors, was splicing itself into YouTube videos dedicated to Fortnite or the animated children’s series Peppa Pig, and even some videos that were pre-approved by the popular YouTube Kids app, to blast harmful messages.

A YouTube spokesperson said the company has seen no evidence of Momo suicide dares spliced into content for children, and these kinds of viral “challenges” are against the company’s terms of service.

“We’ve seen no recent evidence of videos promoting the Momo Challenge on YouTube. Videos encouraging harmful and dangerous challenges are against our policies,” a company spokesperson wrote on Twitter.

A global social media hoax about a paranormal threat to kids morphed into a U.S. viral phenomenon. Patrick T. Fallon / Bloomberg via Getty Images file

The purportedly dangerous meme, however, is a variation of a widespread viral hoax that spread through the Facebook-owned messaging app WhatsApp in South America last July, then moved across India and several countries in Europe before reigniting this week.

Dire warnings about the image, which is a picture of a Japanese sculpture featuring the face of a ghostly young girl atop a bird’s body, began as a chain letter that was sent around the messaging app in Bolivia, Argentina and Mexico last year. Mirroring its trajectory in the U.S., the meme drew various warnings from local police and local news broadcasts about its potential danger, before dying out in less than a month.

Last July, the attorney general of Tabasco, Mexico, issued a warning that receiving messages from people posing as Momo on WhatsApp could result in a wide range of negative consequences, including “theft of personal information, incitement to suicide or violence, extortion, harassment and disorders such as insomnia, anxiety and depression.”

Quickly, however, security experts like Dfndr’s Jeannie Mark denounced it as a “social engineering scheme” that “echoed reports of the Blue Whale Challenge that went viral in 2016, which has been debated as a hoax.”

It’s possible, Mark claimed at the time, WhatsApp users with less strict security settings could receive a message from an unknown account using the photo of Momo as a profile picture, then start any kind of conversation. It’s also possible for strangers to message WhatsApp users with lax security settings with any other kind of photo or name, not just one purporting to be “Momo.”

According to a Google Trends analysis, searches for Momo spiked in Bolivia and Argentina to an all-time high the week of July 15. The top posts queried Google for “Momo historia,” or the meme’s background, “Momo WhatsApp,” and “Momo numero,” as users were searching for "Momo’s" potential phone number.

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Google’s analysis shows the fad faded fast. On Aug. 15, exactly one month after its peak in Bolivia, searches for Momo were back near an all-time low.

According to Daniel Funke, who focuses on misinformation at the journalism nonprofit Poynter Institute, a nonprofit school for journalism, WhatsApp’s features were pivotal in the spread of Momo and other forms of disinformation throughout South America, where the app is heavily used among smartphone owners.

The 'Momo" meme, which supposedly blasted harmful messages to children, turned into a global viral phenomenon. Artur Debat / Moment Editorial/Getty Images

“In terms of WhatsApp, misinformation spreads so quickly in part because it’s so easy to forward things to your friends and family,” Funke said. “Hoaxes spread really rapidly, and it’s hard to combat them since the platform is encrypted—which means not even WhatsApp’s own staff can see what goes viral.”

By that point, the meme had traveled across the world. Stories warning of Momo’s imminent danger were spreading fast across India the week of Aug.12, some using the meme’s scare tactics to make fun of public figures in viral tweets.

Google queries rose in tandem with another viral scare hoax called “Blue Whale,” which began in Russia on the social network VKontakte and was falsely tied to reports of teen suicides.

“Fact-checkers have told me that hoaxes they debunked years ago will still crop up on WhatsApp from time to time because it’s essentially a black box for information sharing,” Funke said.

Searches for Momo in India peaked on Aug. 12 but dithered almost as quickly as they did in South American countries one month before. By Oct. 10, searches for the hoax were back to near all-time lows.

The meme had a similarly rapid rise and fall in France days after it gained prominence in India.

Still, the panic did not reach its peak in the U.S. until this week, when it received a twist: "Momo," the legend said, would randomly appear inside children’s videos on YouTube, and would tell them to commit suicide.

Rumors about Momo swirled around the internet just days after real reports by YouTubers and news outlets showed code words were embedded within some YouTube comments underneath videos on the platform that helped pedophiles better find content featuring young children.

Viral posts about Momo, at times featuring less reliable evidence, took off just days later. On Tuesday, a Twitter user named BreeDaAuraGod_ shared a viral Facebook post about the dangers of Momo. That tweet had since received over 25,000 retweets by Thursday night.

While the existence of videos may have been apocryphal, the rumor spread like wildfire. Local police took to Facebook to warn parents. Schools like the All Saints Day School in Hoboken, New Jersey, sent out an alert to parents about Momo. Even Kim Kardashian West told parents to “please be aware and very cautious” of “a thing called ‘Momo.’”

In reality, videos on YouTube that claim to feature Momo frequently don’t feature Momo at all. Some claim to show Momo in the middle but simply promote rap songs, vlogs or other content not aimed at children.

A similar phenomenon can be seen on Instagram, where users co-opt the virality of hashtags like #momochallenge in an attempt to boost their content, even if the post does not feature Momo.

Warnings about the dangers of Momo videos in the U.S. were heavily promoted on Facebook this week, but not just by trolls and other traditional disinformation agents.

An NBC News analysis using the Facebook metrics platform Crowdtangle revealed the top post on the platform about Momo since Tuesday was a Salt Lake City CBS affiliate’s segment warning parents about Momo. The post, originally published on Tuesday morning, was shared over 350,000 times and featured over 55,000 comments.

“PARENTAL ALERT: A viral challenge encouraging suicide and giving kids tips on how to do it is infiltrating children's video websites like YouTube Kids,” the post reads. A repost of the same segment by a Chattanooga ABC affiliate received almost 23,000 shares.

By Thursday, the story had reached a fever pitch nationwide, receiving segments on CBS News and The TODAY Show, which noted a Snopes story that said Momo’s unexpected appearance in YouTube videos “may be far more hype or hoax than reality.”

Funke called Momo’s ascendence “a feedback loop, in a way,” believing it’s possible the proliferation of the warnings could will a hoax into reality.

He added that there is a real, different lesson parents can learn about the dangers YouTube presents to audiences from the Momo phenomenon: how fast misinformation can stir up a panic online.

“This is a classic case in which misinformers capitalize on a specific audience’s emotions to get more amplification,” Funke said. “In this case, a hoax about a suicide challenge will obviously get traction from parents and older folks.”