Cobb County election officials made a “critical error” and failed to mail over 1,000 absentee ballots to voters who had requested them, the county’s elections director said Friday night.

Most of the voters who weren’t sent their ballots will now have to vote in person on Election Day if they want to participate in the election. The county is mailing ballots by overnight delivery to out-of-state voters, but ballots will only be counted if they’re received back at the county’s elections office before polls close at 7 p.m., according to state law.

Elections Director Janine Eveler wrote in an email to the county’s elections board Friday that election workers didn’t upload ballot information to a mailing machine, and ballots were never created nor sent on two days last month. There were 842 ballots that were supposed to be mailed Oct. 13 and 194 ballots on Oct. 22.

“I am so sorry that this office let these voters down,” Eveler wrote. “Many of the absentee staff have been averaging 80 or more hours per week and they are exhausted. Still, that is no excuse for such a critical error.”

Elections staff couldn’t produce an audit log or a list showing that those ballots had been created, packed or verified, Eveler wrote. She said a new supervisor likely didn’t reference or update procedures.

Of the 1,036 voters who weren’t sent ballots, about 250 of them instead voted in-person during early voting, according to state election data.

Voters who receive their ballots before Election Day can return them at seven county libraries on Saturday and Monday as part of the county’s “last call” absentee ballot return program. Ballots can also be returned at the main county elections office in Marietta before polls close on Tuesday.

Ballot drop boxes are no longer available because they closed at the end of early voting Friday, a requirement of the state’s voting law passed last year.

The American Civil Liberties Union of Georgia called for officials to accept absentee ballots until the ballot return deadline for military and overseas voters on Nov. 14. All other voters must get their ballots in by Tuesday.

Madison Cook, a Cobb resident and student at Mississippi State University who applied for an absentee ballot, said in a statement to the ACLU, “There are many students like me who can’t come home to vote in person.

“I would drive more than 500 miles round trip to vote, but my car is in the shop. Despite my best efforts, it looks like I will be unable to cast a vote in this election.”

Across Georgia, about 279,000 voters requested absentee ballots and 76% of them have been returned. In Cobb, 69% of 30,000 absentee ballots requested have been returned.