(CNN) -- Arizona's Maricopa County listed the wrong date in the Spanish version of voter registration cards, a development likely to further complicate tense relations between local authorities and Latino residents.

The county's elections office says it mailed out nearly 2 million new voter registration cards. Only about 50 of the cards -- handed out over-the-counter at its offices -- had the error, it said.

Instead of Nov. 6, the Spanish translation said the election would take place on Nov. 8.

"The program has been updated so it reflects the correct dates in both English and Spanish," the county said in a statement.

A local rights group said the damage has already been done.

"It's a mistake that should not have happened," Petra Falcon, the executive director of Promise Arizona in Action, told CNN affiliate KNXV-TV. "To know that there's information out there that's wrong, it's going to take a lot of work to make sure that people know the correct date."

Promise Arizona describes itself as "a nonprofit organization dedicated to expanding civic participation in Arizona, particularly among Latinos and youth."

County officials and local Hispanics have long had an adversarial relationship, particularly over the subject of illegal immigration.

Those disputes have landed in court.

In one instance, the American Civil Liberties Union of Arizona and other attorneys are representing Hispanics in a class-action lawsuit accusing Maricopa County Sheriff Joe Arpaio of civil rights and constitutional violations.

The bench trial is being held in the U.S. District Court in Phoenix.

Plaintiffs in the civil case accuse Arpaio -- who bills himself as "America's toughest" -- and his department of racial discrimination against Latinos.

The Mexican American Legal Defense and Educational Fund, and the American Civil Liberties Union of Arizona, are waiting for a federal judge's ruling after a trial of their class-action lawsuit.

Arpaio denies any discrimination.

In a separate matter, the U.S. Justice Department has also accused the sheriff's office of civil rights violations against Latinos.

The sheriff has described the lawsuit against him and the county as politically motivated.

"They're using me for the Latino vote, showing that they're doing something, taking on the sheriff over an alleged racial profiling," he said in May.

Arpaio rejected the Department of Justice's call for monitors to oversee the workings of his department.

 "That shows you they want to take over this office," he said. "Under this agreement with the so-called monitor, I'd probably have to clear every press release before I go public, especially having to do with illegal immigration, with the Department of Justice."

His remarks came after the Justice Department filed the civil lawsuit.

"At its core, this is an abuse-of-power case involving a sheriff and sheriff's office that disregarded the Constitution, ignored sound police practices, compromised public safety and did not hesitate to retaliate against perceived critics," Assistant U.S. Attorney General Thomas Perez said in May.

The Justice Department had delivered in December a report with findings of civil rights violations and sought to fix them through a negotiated settlement with Maricopa County and its sheriff's office. Those talks broke down in February over the county's refusal to consider any agreement that involved an independent monitor, Perez said.

According to the civil complaint, the sheriff's office has displayed a pattern of discrimination against Latinos, which includes racial profiling, unlawful detention and searches, and unlawful targeting of Latinos during raids.

Arpaio has denied any discrimination, and one of his attorneys called the Justice Department investigation a "witch hunt."

CNN's Greg Morris contributed to this report

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