His tweet Thursday amplified a “report” built on empty claims that originated in anonymous comments on a pro-Trump blog.

Trump and his supporters have launched groundless attacks on one of the most widely used technology firms in the U.S., Dominion Voting Systems, seeking to sow doubt in the results of the 2020 election, despite no evidence of any serious irregularities.

Here’s a look at the claims in Trump’s tweet:

TRUMP: “REPORT: DOMINION DELETED 2.7 MILLION TRUMP VOTES NATIONWIDE. DATA ANALYSIS FINDS 221,000 PENNSYLVANIA VOTES SWITCHED FROM PRESIDENT TRUMP TO BIDEN. 941,000 TRUMP VOTES DELETED. STATES USING DOMINION VOTING SYSTEMS SWITCHED 435,000 VOTES FROM TRUMP TO BIDEN.”

THE FACTS: There’s no evidence of widespread fraud in the 2020 election, or of major problems with Dominion’s systems. Election officials from both political parties have stated publicly that the election went well, and international observers confirmed there were no serious irregularities.

“There is no evidence that any voting system deleted or lost votes, changed votes, or was in any way compromised,” says a statement emailed to reporters Thursday by the Cybersecurity & Infrastructure Security Agency, a federal agency that oversees U.S. election security. “The November 3rd election was the most secure in American history.”

Dominion Voting Systems said in a statement that it “denies claims about any vote switching or alleged software issues with our voting systems.”

There have been only a “small handful” of issues that were the result of human error involving voting technology, not the software itself, said Eddie Perez, a voting technology expert at the OSET Institute, a nonpartisan election technology research and development nonprofit.

The OSET Institute has helped monitor more than 1,000 reports of voting issues throughout the U.S. since Election Day.

Perez said he was not aware of any systemic issue related to problems with Dominion software that would affect the tabulation of results.

Technical issues during voting this year occurred at a lower rate than in most elections because “election procedures (were) followed more scrupulously than usual,” said University of Iowa professor Doug Jones, co-author of “Broken Ballots,” a voting technology history.

There is also “no factual basis” for Trump’s claims that 221,000 votes were switched from Trump to Biden in Pennsylvania, Ellen Lyon, spokesperson for the Pennsylvania Department of State, said in an email.

The “report” Trump mentions in his tweet was aired on the conservative television network One America News Network, which promoted a theory posted to a pro-Trump blog that claimed that millions of votes were switched or deleted in Biden’s favor. The TV network did not immediately respond to a request for comment.

The anonymous commenter who posted the theory claimed the findings are supported by data from the polling firm Edison Research. Yet the company has not produced such a report, said Larry Rosin, the president of Edison Research.

“We have no evidence of any voter fraud,” Rosin said in an email.

The biggest example of a tabulation problem in the 2020 election involved a few thousand votes in Antrim County, Michigan, and was the result of human error, Perez said.

When the Republican-leaning county initially reported a landslide win for Biden, social media users grew suspicious about the Dominion election management system used to tabulate the data.

It turned out Dominion was not to blame, according to the Michigan Department of State. “There was no malice, no fraud here, just human error,” County Clerk Sheryl Guy told The Associated Press. The tabulation error was corrected.

Dominion is one of the largest voting technology providers in the U.S., with more than 30 states using its software.

The company has been the target of a number of false claims about the election pushed by Trump supporters, among them that the company has ties to prominent Democrats.