A supporter of Republican presidential nominee Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE was arrested in Texas on Tuesday for allegedly trying to vote twice as part of an effort to “test the system,” the Fort Bend County sheriff’s office said.

Arrest: We can confirm 1 arrested for attempting to vote a second time. Claimed he worked for Trump and was testing the system. — FBCSO Texas (@FBCSO) November 9, 2016

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It’s unclear whether the person, whose identity remains unknown, is an employee of Trump’s campaign or merely a supporter. A spokeswoman with the Trump campaign did not immediately respond to an inquiry.

Trump has previously raised concerns about voting irregularities that he warned may undermine the integrity of the election.

“Of course there is large scale voter fraud,” Trump said earlier this year. "Why do Republican leaders deny what is going on? So naive!"

Studies of in-person voter fraud have found that the practice is incredibly rare. A study published in The Washington Post in 2014 found just 31 credible instances of impersonation fraud out of the more than 1 billion ballots cast between 2000 and 2014.

Supporters of Trump have rallied to monitor polling locations in what they claim is an effort to block efforts to vote illegally.

Trump adviser Roger Stone has launched a project aimed at stopping purported voter fraud, called Stop the Steal, which has recruited volunteers to monitor polls in some Democratic-leaning areas.