In a letter to the Washington Secretary of State's Office, the Justice Department said it had identified 1,500 votes cast by the over 400 people in prior elections. It asked the state to set aside any ballots the people might cast in next month's midterm until state officials can confirm they are legally eligible to vote. The state has more than 5 million registered voters.

"We are asking the state to set aside those ballots until we can confirm they are legal voters," Acting U.S. Attorney Neil Floyd said in a news conference.

Washington Secretary of State Steve Hobbs was reviewing the administration's demand. His office noted that it had received about 60 subpoenas from the Justice Department since last month seeking information about voters.

"We take our responsibility to protect voter information seriously and will only respond to requests that follow due process," Hobbs said in an emailed statement. "We see what's happening in California and don't want Washingtonians to be harassed."