It's unclear whether the roughly 1,500 people mistakenly registered to vote by the Department of Motor Vehicles cast ballots in California's June primary, the state's top elections official said Tuesday.

Secretary of State Alex Padilla said his office is investigating the registration error and working with counties to make sure ineligible people don't vote in the upcoming election Nov. 6, as early voting began this week.

"I remain deeply frustrated and disappointed that persistent errors by the DMV and CDT [California Department of Technology] have undermined public confidence," Padilla wrote in a letter calling for an audit, according to San Diego’s KNSD-TV.

The DMV said the mistakes occurred because of a processing error that affected people who are not legal U.S. citizens, Fresno’s FOX 26 reported.

California held its primary election June 6, while the incorrect registrations happened between April 23 and Sept. 25, according to the DMV.

“These mistakes from the DMV are absolutely unacceptable,” Padilla said. "My concern is it risks jeopardizing confidence in the electoral process."

“These mistakes from the DMV are absolutely unacceptable. ... My concern is it risks jeopardizing confidence in the electoral process." — Alex Padilla, California secretary of state

Padilla said the estimated 1,500 people either told the DMV they were ineligible or didn't confirm their eligibility but were registered anyway.

The group included at least one noncitizen living legally in the state and potentially more. People under 18 or those ineligible to vote because of a criminal conviction could have also been included in error, Padilla said.

The DMV said none of the people mistakenly registered are living in the country illegally. The secretary of state will cancel incorrect registrations, Jessica Gonzalez, a DMV spokeswoman, told KNSD-TV.

People were mistakenly registered through no fault of their own, Padilla said, and his office is removing them from the voter rolls.

DMV Director Jean Shiomoto also said in a statement that the department is working quickly to fix the problem, saying they've "updated the programming and added additional safeguards to improve this process,” the Los Angeles Times reported.

California's motor voter law took effect in April, allowing residents to automatically register to vote through the DMV. Since then, people have newly registered or updated their voter registration more than 3 million times, Gonzalez said.

The Motor Voter program was created to make it easier for people to register, boosting voter turnout. Freezing the program is "certainly on the table," Padilla said.

“We’re doing the homework as we speak of what does that mean and what it would take,” Padilla said at a Tuesday news conference, the San Luis Obispo Tribune reported.

The DMV announced last month it might have botched about 23,000 voter registrations because of a separate error. As a consequence of the mistake, the department sent the secretary of state's office incorrect information for some voters. The error mostly affected people's vote-by-mail, language and political party selections, according to the department.

The DMV found out about the roughly 1,500 mistaken registrations after the L.A. Times' Monday report on a Canadian who was registered incorrectly. The green card holder contacted the Times on Sept. 30 because he received a voter registration notice in the mail after trying to replace his driver's license at the DMV, according to the paper

“When I saw that card, I just threw it out,” Marquis said. “I know I’m not going to vote. I’m not allowed to vote, it’s stupid that I should be registered to vote,” he told the Times.

The DMV and Padilla's office didn't specify how many noncitizens were registered.

The Associated Press contributed to this report.