Ohio investigators are treating a warehouse where 15 electronic voting machines have been quarantined as a crime scene following a report someone may have illegally tampered with them to remove a candidate's name from the ballot.

Officials from Ohio's Franklin County Board of Elections asked for a forensic analysis of the touch screen machines after Secretary of State Jennifer Brunner reported seeing something she regarded as odd while voting during last November's election: A gray bar and the words "candidate withdrawn" appeared where candidate Jay Perez's name should have been. Brunner's husband, who was using a nearby machine at the same time, said Perez was on his ballot.

"This is a huge problem," Brunner told The Columbus Dispatch. "There is great concern that not every voter has the same ballot."

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Investigators have already found that last April someone manually disabled a logging feature in Franklin County machines that is designed to help officials track unauthorized changes to the devices. They also found that many of the machines hadn't been tested prior to the November election, according to preliminary results submitted by SysTest Labs, a Colorado quality assurance and testing company.

Ohio has a checkered history with elections. Two state elections officials were convicted of rigging a 2004 recount after admitting to doing precounts and displaying the evidence while being videotaped. Last year, a study commissioned by Brunner's office found state e-voting machines contained critical security failures that could jeopardize the integrity elections.

Brunner alerted the director of the Franklin County Board of Elections of the missing candidate a few days after the election and officials promptly pulled every suspect machine to check the ballots. Perez's name was listed on each one. Officials have also checked ballots and paper tapes, but have also found no evidence to support Brunner's account.

But she says there are reports from other precincts of voters seeing the same "candidate withdrawn" words on their machines.

Brunner has conceded investigators may never learn what really happened.

Separately, Princeton University Ed Felten said e-voting machine seller Sequoia Voting Systems has threatened him and a fellow researcher if they conduct an investigation into vulnerabilities into devices submitted by the state of New Jersey for testing. "We will also take appropriate steps to protect against any publication of Sequoia software, its behavior, reports regarding same or any other infringement of our intellectual property," a Sequoia attorney wrote, Felton reports.