President Donald Trump claimed that Muslim prayer rugs are being found on the U.S.-Mexico border in a tweet Friday, dredging up a long-running, discredited right-wing internet rumor.

Citing a Washington Examiner story that ran on Wednesday, Trump tweeted that the identities of some people crossing the border would be a “big surprise.”

“Border rancher: ‘We’ve found prayer rugs out here. It’s unreal.’ Washington Examiner,” Trump tweeted. “People coming across the Southern Border from many countries, some of which would be a big surprise.”

The Examiner story that Trump cited has stirred up the pro-Trump internet, getting picked up on sites like Jihad Watch and WorldNetDaily.

In the past, though, claims of border-region prayer rugs have been quickly disproven, and there’s no reason to believe the Examiner is more credible.

The Examiner article is based on only one source: an anonymous Arizona rancher who wouldn’t let the reporter use her name out of “fear of retaliation by cartels.”

“We’ve found prayer rugs out here,” the rancher said. “It’s unreal. It’s not just Mexican nationals that are coming across."

The Examiner story doesn’t include any photos of the supposed prayer rugs.

The story also doesn’t provide any explanation for how the rancher knows that they’re prayer rugs, rather than a blanket or clothes. In one video, the rancher said she hasn’t seen any of supposed immigrants who supposed to be bringing the rugs.

The rancher’s stories has other issues, too. At one point in the video, she claims that the area around her ranch is seeing illegal immigration from Czechoslovakia.

“Those Czechoslovakians, they cut over on our neighbor this last summer,” the rancher says in the video.

It would be impossible for Czechoslovakians to immigrate to the United States, illegally or not, because Czechoslovakia ceased to exist 25 years ago.

The story’s author, Examiner reporter Anna Giaritelli, didn’t respond to a request for comment. Giaritelli is the former press secretary for the Federation for American Immigration Reform, which is classified as a hate group by the Southern Poverty Law Center for its leaders’ “ties to white supremacist groups” and “many racist statements.”

The idea of prayer rugs popping up on the border dates back to at least 2005, when congressional Republicans pushed the rugs as proof that terrorists were attempting to infiltrate the U.S. from Mexico.

Even the original reports of prayer rugs were thinly sourced. In 2005, Sen. Kay Bailey Hutchison (R-TX) claimed in a speech on the Senate floor that prayer rugs and notebooks filled with Arabic writing were being discovered in border regions. But Hutchison didn’t offer any proof of the rugs, saying that she had heard of them only as “stories of suspicious items picked up by local residents.”

Since then, the idea of prayer rugs being discovered on the border as proof of a terrorist invasion has recurred every few years on the right.

In 2014, Breitbart published a story touting the discovery of a “Muslim prayer rug” in Arizona. But a picture of the “prayer rug” showed that it was just a torn Adidas jersey.

Asked about whether the shirt was a prayer rug, one Middle East expert replied: “Is this a joke?”

That same year, Texas Lt. Gov David Dewhurst (R) claimed that prayer rugs were being discovered in the brush in Texas. PolitiFact rated that statement “pants on fire,” after checks with Border Patrol and other law enforcement officials on the border failed to turn up any proof of prayer rugs.