CHICAGO (AP) — In the days since President Donald Trump blamed antifa activists for an eruption of violence at protests over police killings of black people, social media has lit up with false rumors that the far-left-leaning group is transporting people to wreak havoc on small cities across America.

The speculation was being raised by conservative news outlets and pro-Trump social media accounts, as well as impostor Facebook and Twitter accounts.

Twitter and Facebook busted some of the instigators behind the unsubstantiated social media chatter. Twitter determined Monday that a tweet promising antifa would “move into residential areas” and “white” neighborhoods was sent by the white supremacy group Identity Evropa. The tweet was shared hundreds of times and cited in online news articles before Twitter removed it Monday, a company spokesperson said.

Yet the tweet continued to circulate Tuesday on Facebook and Instagram.

Facebook, using information shared by Twitter, announced Tuesday night it also took down a handful of accounts on its platform that were created by white supremacy groups like Identity Evropa and American Guard, some of them posing as part of the antifa movement.

For years, some social media users have tried to delegitimize controversial or political protests with baseless theories that they were organized by wealthy financiers or extremists organizations. Over the weekend, Trump singled out antifa as being responsible for the violent protests triggered by the killing of George Floyd, saying in a tweet: “It’s ANTIFA and the Radical Left.”

“Usually you see this when there’s an interest to deflect conversations from protests to just accusing the protests of being violent, organized or having backers that are evil,”said Filippo Menczer, a professor of informatics and computer science at Indiana University. “The president mentioning it, of course, has generated a huge spike.”

The theories about antifa — short for “anti-fascists” and an umbrella term for lefitst militant groups that confront or resist neo-Nazis and white supremacists at demonstrations — have trickled through cities across the country in recent days.

Police departments say people are phoning in “tips” they see on social media claiming antifa is sending buses or even planes full of antifa activists to their area.

In Payette County, Idaho — a rural county of 24,000 — the calls started early Monday morning after one Facebook user said the sheriff had spotted antifa rioters in the area. The calls didn’t taper off until the sheriff’s office debunked the rumor on Facebook.

“It’s really a small community, where our citizens know us pretty well,” said Payette County Sheriff Lt. Andy Creech. “When the post got out there, we started getting phone calls directly.”

Meanwhile, Facebook users were also warning their friends to stay clear of a shopping center in a New Jersey suburb, saying it would be the center of antifa destruction on Tuesday.

But police had “no credible information” that antifa would be present in the area, Toms River Police Department media specialist Jillian Messina said in an email. The police aren’t aware of anyone showing up at all, she added.

Identical Facebook and Twitter posts about busloads of antifa protesters also stumped the Sioux Falls Police Department, where officers in the South Dakota city said they didn’t see any unusual bus activity in town. But the claims still spread for days ahead of a planned protest this Saturday, said Sam Clemens, a public information officer for the department.

“Everyone heard there were going to be buses of people,” Clemens said. “It was very specific: there were three busloads.”

Even the owner of a Michigan limousine business was forced to refute online rumors when two of his buses became the center of a conspiracy theory that liberal financier George Soros was funneling protesters to Milan, Michigan. Social media users widely shared a manipulated photo of his white buses, edited to show the words “Soros Riot Dance squad” emblazoned on the sides.

The buses belong to Sean Duval, the owner of local transportation company Golden Limousine International, and don’t have any words printed on them.

Said Duval: “It’s frustrating when people from the outside start instigating and try to turn American against American.”

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Associated Press writers Barbara Ortutay in Oakland, Calif., Beatrice Dupuy in New York and Ali Swenson in Seattle contributed to this report.