Scott Leiendecker, the Republican director for the St. Louis Election Board, said officials believe the ballot was filled out by the woman's son, who apparently signed the ballot with an "X" and signed his own name as a witness, the St. Louis Post-Dispatch reported Wednesday. The woman has been dead since October.

Leiendecker said the case has been turned over to the Department of Justice. He said the alleged fraudulent ballot was one about 2,000 absentee ballots cast in the city, the newspaper reported.

The official said the incident illustrates the success of the city's voter fraud prevention system.

"I think the message is out there that this is not something to joke about," Leiendecker said. "We have really good people watching and have good checks and balances in place."