Hispanic leaders in Tarrant County have filed a complaint with the U.S. Justice Department, alleging that senior citizens are being intimidated into not voting.

The Fort Worth Star-Telegram reports that the complaint from the United Hispanic Council of Tarrant County says a voter fraud investigation has "left a trail of confused and upset seniors who are now afraid of voting," either in person or by absentee ballot.

Concerns have arisen over mail-in ballots, which some people think can lead to "vote harvesting" — the illegal process of filling out and returning the ballots of valid voters without their consent.

The complaint alleges that political activists are making "vigilante-style" door-to-door visits, claiming to be investigating voter fraud.

"This is voter suppression," Fort Worth Councilman Sal Espino told the Star-Telegram. "When these people go talk to seniors, they are accusing them of doing something wrong, making it seem as though they shouldn't have voted by mail."

Mail-in ballots are designed for voters who are unable to leave their homes, are in jail or out of the country.

Supporters argue that such ballots are critical for people who cannot vote by other means. But critics say the process allows people to vote without verifying their identities, thereby opening the door for abuse.

Aaron Harris, a Republican political consultant, has led anti-voter-fraud efforts in Tarrant County and is promoting an "Election Integrity Tip Hotline" that offers a $5,000 reward for information that leads to a conviction.

After learning of the United Hispanic Council's complaint, Harris took to Facebook, posting: "So I expose the fraud, and those who are stealing the votes and suppressing voters want to sue me."

The Justice Department said it had not received the complaint and could not comment at this time.

Claims of electoral fraud have swirled this year, kindled by Republican presidential nominee Donald Trump's repeated claims of vote-rigging.

The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary - but also at many polling places - SAD — Donald J. Trump (@realDonaldTrump) October 16, 2016

But experts have said that voter fraud is incredibly rare, with one study finding 31 instances of voter impersonation from 2000 to 2014 — a period when more than 1 billion ballots were cast.

Some observers say investigations of alleged voter fraud are motivated by politics, while others think such probes are tackling a pervasive issue.

"The Republicans have been looking for a blockbuster case to demonstrate that voter fraud isn't just a series of small mistakes," Brandon Rottinghaus, a political science professor at the University of Houston, told the Star-Telegram. "If some of these allegations turn out to be true, they may finally have their white whale."