U.S. District Judge Araceli Martínez-Olguín said the investigations should stop until polls close on Election Day, Nov. 3. She put the ruling on hold until Friday to give the administration time to appeal, leaving its immediate effect subject to that process.

The order covers California, Connecticut, Georgia, Missouri, Nevada, New York, Pennsylvania, Washington and Wisconsin. The investigation, called the Unlawful Voter Initiative, is part of a broader administration effort to identify noncitizens who may be registered to vote. Noncitizens are not eligible to vote in federal elections, but the report notes that such voting is rare, including in the administration’s own investigations.

Martínez-Olguín wrote that the lists investigators used were “voluminous and unreliable.” There is no federal database that establishes the citizenship status of U.S. residents, she said, increasing the chance that people would be wrongly flagged. During a rapid-review phase that began in late August, agents were instructed to spend no more than 12 minutes assessing each person identified for scrutiny.

Court filings said investigators were directed to examine naturalized citizens to determine whether they had voted before becoming U.S. citizens. The lists drew on state and local government records as well as publicly available information. Where states declined to provide voter records to the federal government, the administration sought commercial versions of voter-roll data, which the judge also described as unreliable.

The plaintiffs — the California Nurses Association, National Nurses United, Voto Latino Foundation, San Francisco and Santa Clara County — argued that U.S. citizens had been wrongly identified and investigated. Martínez-Olguín said the investigations had created fears she characterized as intimidation, discouraging some people from attending campaign events or serving as poll monitors.

Beau Tremitiere, an attorney for the plaintiffs, said the ruling supported their claim that investigators relied on faulty information and sent agents to people’s homes shortly before an election without adequately checking the data.

The Department of Homeland Security said in an email statement that it was focused on “removing aliens who vote and dilute the votes of U.S. citizens.” The department added that it had no plans to question or investigate people it believed to be U.S. citizens.

The case was filed as the Justice Department has sought detailed, unredacted voter-registration records from states. The investigation’s details became public last month after Senate Democratic leader Chuck Schumer of New York and Sen. Alex Padilla of California released a whistleblower report about the initiative.