A Houston woman says she was turned away from the polls because a so-called “mystery voter” had already cast a ballot in her name.

Angie Medellin, 72, said she went to turn in her mail-in ballot Thursday at a polling center in the East End neighborhood, news station KHOU reported.

But when she got there, she was told by election workers that the system said she had voted two weeks earlier at a different location.

“She just said, ‘Well, you voted,’ and she was insistent that I voted,” Medellin said of her conversation with the poll worker.

Medellin said the other location was nine miles away and records showed that she had used a driver’s license to vote.

“I don’t own a driver’s license. Never have, I don’t drive,” said Medellin, adding that she has only had a state ID card.

Incoming Harris County election administrator Isabel Longoria said the mix-up was a “one-in-a-million” incident.

Longoria said what she believes may have happened was a mix-up where the so-called “mystery voter” didn’t bring a scannable form of identification.

Instead, the poll worker likely manually entered the person’s name without double-checking the address with them to make sure it was the correct voter information.

Longoria said there are around 250 other registered voters in the county with the last name “Medellin” and first initial “A.”

“You got to confirm the address,” Longoria said. “You have to confirm the details on that signature page are yours.”

Medellin will be allowed to cast a provisional ballot and election officials will notify the early-vote ballot board of the error, the outlet reported.

Meanwhile, election officials will be going through that list of other voters with the same last name and first initial to compare signatures and track them down, KHOU reported.

Longoria said they will also be retraining staff on proper procedures.

“That’s not our standard at the Harris County Clerk’s Office. Our standard is to protect every single voter, one or 1 million,” Longoria said.