Washington — Homeland Security Secretary Markwayne Mullin on Friday continued to amplify President Trump's assertion that more than a quarter of a million noncitizens were registered to vote in four states, though the administration has yet to provide details of how it arrived at that figure.In a news conference following Mr. Trump's address to the nation Thursday that focused on election security, Mullin said the alleged 250,000 noncitizens that it believes were registered to vote were in California, Pennsylvania, New Jersey and Nevada. Those four states have not complied with the Trump administration's demands to provide voter data to the federal government. In 23 states that are working with the Trump administration and ran their voter records through an overhauled centralized federal database, Mullin said an additional 28,000 noncitizens were registered to vote.But CBS News found that the claims from Mr. Trump and Mullin about the prevalence of noncitizens registering to vote could be exaggerated. The estimate that there are 250,000 noncitizen registered voters across four states was based on an analysis of commercial databases, a White House official told reporters Thursday. That method is likely to lead to false positives, significantly overestimating the number of potential noncitizens on voter rolls, David Becker, executive director and founder of the Center for Election Innovation and Research, said during a CBS News special report Thursday."I guarantee you, that data includes a ton of people, maybe even a majority of people, who are absolutely eligible voters, and states would probably be breaking the law if they remove those voters from the rolls," Becker said.The Center for Election Innovation and Research has found that allegations of noncitizens casting ballots or registering to vote typically "appear to arise from misunderstandings, mischaracterizations, or outright fabrications about complex voter data." When those claims are scrutinized and investigated, the number of alleged instances of noncitizens identified on voter rolls drops, the group said. Confirmed cases of noncitizens voting are exceedingly rare.