Lawmakers in Pennsylvania last year approved the use of voting by mail, but it remains unclear if the state would utilize the approach in a presidential election this year.

“We looked for three decades for all the instances of voter fraud," researcher Matt Barreto of UCLA's Voting Rights Project told NBC10 in an interview. "These have actually been tabulated and catalogued. We found that it's just not happening in vote by mail."

The call for voting by mail in Pennsylvania and other states has arisen as the coronavirus has forced most of the country to stay inside their homes. It remains unclear when people will be able to resume a public life.

Pennsylvania and New Jersey are among the states who have already postponed their primary elections. The general election in November is expected to have the largest turnout since the last presidential election four years ago. There has been no declaration that an entire election would be mail-in, but states already utilize the mail-in option to allow absentee voting.

Pennsylvania Secretary of State Kathy Boockvar, who oversees elections, said she is very confident that voting by mail wouldn't increase the chances for voter fraud.

"Absolutely. 100%," Boockvar said of her confidence in election security involving a vote by mail.

"I would prefer people vote by mail -- this year," she said. "For this time period because again you’ve got the safety built in. You can do it on your schedule from the security and comfort of your home."

The Heritage Foundation, a conservative thinktank, keeps track of all instances of voter fraud in the United States. Its database goes back more than 40 years. In thousands of elections involving hundreds of millions of votes, it has tallied 213 instances of voter fraud related to mail-in ballots.