The Department of Justice announced Monday that investigators have identified more than 400 noncitizens who are illegally registered to vote in Washington state. According to the U.S. attorney's offices for the Eastern and Western districts of Washington, some of them have cast ballots in multiple elections stretching back decades.

Many of those on the list are green card holders who have legal immigration status and permanent residency. "We have identified over 400 noncitizens who are registered to vote and have voted in multiple elections. This is only the tip of the iceberg," said Neil Floyd, acting U.S. attorney for the Western District of Washington. He added that his office will keep investigating those who commit crimes by voting illegally.

In an interview with Fox News Digital, Floyd explained that investigators found the voters by reviewing records from U.S. Citizenship and Immigration Services. Those records showed that some people who applied for certain benefits had also voted. Some individuals voted once or three times, while others voted as many as 27 times. His office counted roughly 1,500 instances of noncitizens casting ballots. Floyd said the earliest case he knows of dates to 1984, before Washington moved to a vote-by-mail system.

Floyd said he had not checked whether any of the individuals voted in the upcoming midterms, because he did not want to "interfere with the current election." He also cautioned that the figure may capture only a fraction of the problem, since the list covers only people who sought certain benefits in Washington. Expanding it to include others in the country illegally with whom officials have had no contact, he estimated, "is going to be in the thousands."

Federal officials said many green card holders were registered without their knowledge through Washington's Motor Voter program, which builds voter registration into the state's Department of Licensing. The DOJ notice said some of these residents then received a ballot in the mail and assumed they were legally registered, which it said was not the case. The Washington secretary of state's website says eligible residents are automatically registered only if they provide proof of U.S. citizenship while getting a driver's license or ID card. Floyd said the findings have helped officials identify patterns in how the registration process failed.

The notice asks Washington to set aside ballots cast by the identified individuals until their citizenship can be confirmed. "Washington is now on notice that noncitizens are voting," it said, adding that it is up to the state to ensure they are not allowed to vote illegally.

Officials warned that voting as a noncitizen can carry serious consequences for people seeking U.S. citizenship. Possible criminal charges include making false statements in a naturalization application, and some individuals could also face charges for fraudulent voter registration.

The announcement follows DOJ legal action against Los Angeles County, where the department has sought to set aside about 20,000 mail-in ballots sent to people whose citizenship status is in question.

Separately, the Department of Homeland Security told Fox News Digital on Tuesday that dozens of noncitizens have been arrested nationwide in a voter fraud crackdown. Numerous people had admitted to unlawfully registering or voting in U.S. elections, and at least 18 of the suspects had voted in a federal election. They came from countries including Mexico, Somalia, Honduras, Guyana, Cuba, Germany, Nicaragua, Venezuela, Vietnam, El Salvador, Cambodia, Guatemala, Portugal and Italy. Many also faced charges for other alleged crimes, among them counterfeiting, fraud, kidnapping, DUI, sexual offenses, assault with a dangerous weapon, drug possession and burglary.