SPRINGFIELD, Ill. (NEXSTAR) — The Illinois State Board of Elections acknowledged that out of 574 non-U.S. citizens who were inadvertently registered to vote in Illinois, an unknown number of them may have voted illegally in the 2018 election.

“We do know that some of them voted” in the 2018 election, spokesman Matt Dietrich said in a phone call on Monday afternoon, though his office was not immediately able to determine how many of them may have voted, or how many may have been legal citizens who simply filled out their state form incorrectly. Dietrich expects the elections agency will have more specific answers when state workers return to their desks after a government holiday.

Update: 10:48 a.m. The State Board of Elections says 19 people who self-identified as non-citizens voted in Illinois in 2018.

Update: the State Board of Elections says out of the 547 non-citizens, 19 of them voted in 2018. Working now to confirm their exact location. Macon County Sheriff's race was decided by just one vote in 2018. 7 of the 547 non-citizens were registered in Macon County. https://t.co/pmJd3N5kSZ — Mark Maxwell (@MarkMaxwellTV) January 21, 2020

Secretary of State Jesse White’s office admitted it was at fault for the “isolated” incident, and offered assurances that the “programming error” in the state’s new automatic voter registration process has since been repaired.

Illinois law allows immigrants who are not citizens to get a driver’s license or state identification. Both state and federal law prohibits non-citizens from participating in American elections.

White’s office sent a letter to the State Board of Elections on December 18th notifying them that despite several safeguards, a programming malfunction in the agency’s electronic keypads improperly registered 574 non-American citizens to vote.

“For whatever reason that technological programming error did not properly remove the individuals,” Secretary of State spokesman Henry Haupt explained. “The individuals who are applying for driver’s license were inadvertently pooled into the automatic voter registration.”

That error likely triggered a steady stream of pamphlets, post cards and mailers to invite the non-citizens to vote. Once a person is registered to vote, their name and information is made a part of public record. Local election officials routinely mail voting instructions to the household, and political campaigns send them advertisements persuading them to vote for specific candidates or causes.

It remains unclear how many of the 574 people impacted may have actually cast a ballot in 2018, in part, because state employees at the elections board couldn’t be reached on a state holiday. A spokesman for the agency expects to have a more specific answer on Tuesday. Non-citizens who vote in American elections can face swift consequences, including immediate deportation.

“If that person voted, that’s a huge problem when it comes to the federal government,” state Representative Tim Butler (R-Springfield) warned on Monday. “That’s a deportable offense for this person. And if that’s the case, that’s something that’s on the Secretary of State’s office for allowing that offense to happen.”

Although some elections were decided by just a handful of votes in 2018, including the Macon County Sheriff’s race that came down to one vote, there is no available evidence that would suggest an outcome of an election was altered.

In a letter written to White’s longtime political ally House Speaker Michael Madigan (D-Chicago), Butler and four other House Republicans called for White and the State Board of Elections to testify before investigative hearings in the House Executive Committee. Madigan’s office has not yet responded to a request for comment.

“We have to have complete confidence that our offices are doing the right thing,” Butler said. “And that goes for the Secretary of State. He may or may not have known about this. I have no idea. But he needs to be held responsible for it. It’s his operation that allowed this to happen.”

“We discovered an error, and we fixed it,” Haupt said. “And then we notified the State Board of Elections and the local election authorities and the individuals that were impacted.”

The Illinois primary election is on March 17th. Early voting begins on February 6th. Local election authorities have been informed which non-citizens were improperly registered to vote, and have been instructed to remove their names from the voter rolls.