Jerry Mosna was gardening outside his San Pedro, Calif., home Saturday when he noticed something odd: Two stacks of 2016 ballots on his mailbox.

The 83 ballots, each unused, were addressed to different people, all supposedly living in his elderly neighbor’s two-bedroom apartment.

“I think this is spooky,” Mosna said. “All the different names, none we recognize, all at one address.”

His wife, Madalena Mosna, noted their 89-year-old neighbor lives by herself, and, “Eighty people can’t fit in that apartment.”

They took the ballots to the Los Angeles Police Department, but were directed to the post office. They felt little comfort there would be an investigation, and called another neighbor, John Cracchiolo – who contacted the Los Angeles County Registrar's office.

A spokeswoman for the Registrar said the office will investigate. Both Cracchiolo and Jerry Mosna told FoxNews.com they think they stumbled upon a case of fraud.

“Yes, there is voter fraud. We saw it with our own eyes,” Cracchiolo said.

In a statement, the office of the Registrar said, “We are carefully reviewing our records and gathering information to fully identify what took place. Our preliminary assessment is that this appears to be an isolated situation related to a system error that occurred causing duplicate ballots to be issued to an address entered for a single voter. We are working directly with the system vendor to ensure the issue is addressed and to identify any similar occurrences.”

Further, spokeswoman Brenda Duran said the Postal Service “has indicated that they returned all of the improperly addressed ballots to our office.”

Spokesman Richard Maher confirmed the U.S. Postal Inspection Service has offered its assistance. He would not comment on the number of incidents, saying only there are “relatively few.”

John Fund, a journalist and co-author with Hans von Spakovsky of the book, “Who’s Counting: How Fraudsters and Bureaucrats Put Your Vote at Risk,” said someone could easily have voted with these ballots using a variety of fake signatures.

“It is doubtful they would have ever been detected,” Fund said.

Von Spakovsky, senior legal fellow and manager of the Election Law Reform Initiative at the Heritage Foundation, said voter fraud is prevalent enough that it could make the difference in a close election. The Heritage Foundation, he said, has recorded 430 cases of voter fraud -- proven cases where someone was convicted or a judge ordered a new election.

A former FEC commissioner and counsel to the assistant attorney general for civil rights at the U.S. Justice Department, von Spakovsky said California is of particular concern because of the rising number of noncitizens illegally registering and voting in elections, as well as the “terrible shape” the voter registration rolls are in.

The 89-year-old neighbor to whom the stack of ballots was addressed is hard of hearing, and was unavailable for comment. The Mosnas stressed that the ballots clearly were not for her -- and have not even discussed the issue with her.