Dozens of 17-year-olds voted illegally across Wisconsin during last spring's intense presidential primary, apparently wrongly believing they could cast ballots if they turned 18 ahead of the November general election, according to a new state report.

Wisconsin Elections Commission staff examined voter fraud referrals municipal clerks said they made to prosecutors following the 2016 spring primary and general elections. The commission is set to approve the findings during a meeting Tuesday and forward a report to the Legislature.

President Donald Trump has called for a "major investigation" into voter fraud and alleged that 3 million to 5 million people may have voted illegally in the November general election, a widely debunked claim. The report lists no instances of underage voters casting ballots in the general election.

Republican Ted Cruz won the GOP primary in Wisconsin. Bernie Sanders won the Democratic contest. The state ultimately voted for Trump in the November general election, marking the first time a Republican presidential candidate had won Wisconsin since Ronald Reagan in 1984.

The report found at least 60 cases of 17-year-olds voting in the April primary in 29 counties. Kewaunee County referred nine people to prosecutors for voting as 17-year-olds, Rock County referred seven and Racine County referred five. Brown County referred what the report called "multiple" 17-year-olds to prosecutors. The report did not track charging decisions or for whom the 17-year-olds voted.

Commission spokesman Reid Magney said Monday that he'd never seen this issue crop up before. The teenagers were likely encouraged to go to the polls by messages flying around social media during the spring primary season saying 17-year-olds can vote in some states as long as they turn 18 before the November election, the report said.

Some political campaigns were also spreading false information about eligibility, the report said. The Sanders campaign specifically was sending out national messages on social media about 17-year-olds being able to vote in presidential primaries, Magney said, although Wisconsin election officials didn't see any misinformation from that campaign about Wisconsin.

No one under 18 can vote in any Wisconsin election, but 17-year-olds may have seen Sanders' messages and thought they could vote. Poll workers may not have understood the law or may not have been paying enough attention, he added.

"It wasn't a case of anyone sneaking in," Magney said. "It was a misunderstanding of the law."

Sanders campaign officials didn't immediately respond to an email Monday seeking comment.

Kewaunee County District Attorney Andrew Naze said he chose not to charge any of the 17-year-olds whom clerks referred to him. He said they honestly thought they were eligible to vote and didn't intend to break the law.

Brown County District Attorney David Lasee said nine 17-year-olds were referred to him but he decided not to file charges as well. Like Naze, Lasee said the teens genuinely believed they could vote and there was no intent to commit fraud. They told poll workers their ages and were still allowed to cast ballots, Lasee said.

Prosecutors in Rock and Racine counties didn't immediately respond to messages Monday.

The report noted that its findings aren't conclusive and it's possible other instances of suspected fraud may have been referred to prosecutors without the commission's knowledge or people may have filed complaints directly with district attorneys.