Hundreds of voters in St. Louis County, Missouri received letters from election officials in October erroneously telling them they were ineligible to vote in next week's midterm election.

The letters were sent out in mid-October, near the Oct. 10 registration deadline, Eric Fey, Democratic Director of Elections, told Fox News on Thursday.

MISSOURI HOUSE CANDIDATE'S CHILDREN URGE PEOPLE TO NOT VOTE FOR THEIR FATHER

It was reported by the St. Louis Post-Dispatch that 600 voters were told they couldn't vote on Nov. 6. However, Fey said it was "probably not" 600, and added the board will have a firm number by the end of day Thursday.

The erroneous letters were sent after election workers were confused by Missouri's voter registration laws, according to the official. The state allows residents to register to vote through mail if their form is postmarked by Oct. 10.

Even if the voter registration is received by election officials after the registration deadline, as long as it's postmarked by the 10th, registrations are still accepted.

HURRICANE MICHAEL COULD IMPACT VOTER TURNOUT IN FLORIDA PANHANDLE

The board, according to the Post-Dispatch, sent letters to roughly 1,500 people informing them their registration was received too late, and that they couldn't vote next week. Around 600 of those were reportedly valid registrations.

Several people who received such letters called the election board right away, Fey told Fox News. The election official said the office "corrected all these errors," and is sending a corrective letter to voters who had not inquired about their registration status.

The election board's website, whether in a posting or news release, does not mention the error. Fey said this was because the board doesn't "want to needlessly alarm other voters about it."

Anyone who has been affected by this error will hear from the election board personally, he said.

Those with questions or concerns can call the St. Louis County Board of Elections at 314-615-1800.