Arizona’s top elections official said Tuesday that a newly identified error in the state’s voter registration process needs to be swiftly resolved, as early ballots are set to go out to some voters as soon as this week.

Election staff in the Maricopa county recorder’s office identified an issue last week, which concerns voters with old drivers licenses who may never have provided documentary proof of citizenship but were coded as having provided it and therefore were able to vote full ballots. The state has a bifurcated system in which voters who do not provide documentary proof of citizenship cannot vote in local or state elections, only federal ones.

Because of the state’s very close elections and status as a swing state, the issue affecting nearly 100,000 voters will likely be the subject of intense scrutiny and litigation in the coming weeks. Arizona has more than 4.1 million registered voters.

Governor Katie Hobbs directed the motor vehicles division to fix the coding error, which the secretary of state, Adrian Fontes, said was already resolved going forward.

It’s not clear if any of these voters have unlawfully cast a ballot or if they have already provided proof of citizenship. People who register to vote check a box on registration forms, under penalty of perjury, declaring they are citizens.

“We have no reason to believe that there are any significant numbers of individuals remaining on this list who are not eligible to vote in Arizona,” Fontes said in a press conference Tuesday. “We cannot confirm that at this moment, but we don’t have any reason to believe that.”

The error, reported by Votebeat on Tuesday, relates to several quirks of Arizona governance.

Since 1996, Arizona residents have been required to show proof of citizenship to get a regular driver’s license. And since 2004, they have been required to show proof of citizenship to vote in state and local elections.

State drivers licenses also do not expire until a driver is age 65, meaning for some residents, they will have a valid license for decades before needing renewal. These factors play into the error.

The issue has split the Republican recorder in the state’s largest county, Maricopa, and the Democratic secretary of state. Recorder Stephen Richer is arguing that these voters should only be able to cast a federal-only ballot, while Fontes says the state should keep the status quo of allowing them to vote full ballots given how soon the election is. Fontes directed counties to allow these residents to cast full ballots this year.

Arizona is home to a strong election denial movement, and the issue is likely to play into these narratives. Republicans have for months been stoking fears about non-citizens voting in the November election in Arizona and nationwide, despite a lack of evidence that non-citizens are voting in any meaningful numbers.

Richer wrote on X that his office would be suing Fontes’s office over this, saying because they disagree, the courts will provide “a clear answer”. Richer’s office identified the issue, which affects all counties in the state. The lawsuit was filed Tuesday afternoon, and in it, the recorder’s office said it had discovered the issue by identifying a non-citizen who was erroneously registered to vote, though the person had not cast a ballot in the past.

“All of these people have attested under penalty of law that they are U.S. citizens. And, in all likelihood, they [are] almost all U.S. Citizens,” Richer wrote on X, adding that they had not provided proof.

The group in question contains approximately 98,000 voters. Fontes said the “plurality” of these residents are Republican and between ages 45 and 60, receiving driver’s licenses before 1996.

“If you are on this list, rest assured you will be contacted soon by Arizona elections officials,” Fontes said Tuesday. But, he added, elections offices first want the courts to weigh in before reaching out to voters “willy-nilly”.

As described by Votebeat, the problem relates to people who “first obtained their Arizona driver’s license before October 1996 and then were issued a duplicate replacement before registering to vote sometime after 2004”.

Elections officials would look at voter registration forms to see when licenses were updated to see if the dates meant people had submitted the required proof of citizenship. For dates after October 1996, officials assumed paperwork was in order. But, unbeknownst to elections officials, the motor vehicles division’s system would update the license issuance date when people replaced or updated their licenses, making it look like the license was newer and would have included proof of citizenship.

The error has occurred, seemingly unnoticed, since 2005, the lawsuit says.