New Jersey Attorney General Gurbir Grewal says a Paterson city councilman, a councilman-elect and two other men face criminal voting fraud charges stemming from the May 12 special election in the city.

Grewal said Thursday the investigation began when the U.S. Postal Service’s law enforcement arm told the attorney general’s office about hundreds of mail-in ballots located in a mailbox in Paterson, along with more found in nearby Haledon.

It’s unclear what about the ballots tipped officials off to the possibility of a crime, as well as how the alleged wrongdoing unfolded.

Grewal doesn’t say whether the allegations affected the outcome of the election.

AP wire services helped contribute to this report.