The US Justice Department has given California officials 48 hours to review a list of people suspected of being non-US citizens who were sent mail-in ballots, warning that it could seek emergency legal action if the state does not comply, according to the letter reviewed by Reuters.Acting Deputy Attorney General R. Trent McCotter sent the letter to California Secretary of State Shirley Weber on Tuesday. It said federal authorities had shared a list of suspected noncitizens with officials in Los Angeles County on a password-protected thumb drive.The letter directs state officials to withhold ballots from those individuals until their citizenship status is verified. For ballots already issued, officials were instructed to keep returned ballots separate and refrain from counting those already submitted until citizenship had been determined.The department warned it would have “no choice but to seek emergency relief” if California officials failed to follow the instructions.“Allowing noncitizens to vote cancels citizen votes,” McCotter wrote.Justice Department spokeswoman Kiersten Pels confirmed the letter in a statement to Reuters, saying the department would take “all necessary legal action to protect election integrity and ensure compliance with federal law”.The demand comes as the Trump administration increases pressure on states over allegations that non-US citizens are voting in US elections.Last month the news agency reported that software glitches and clerical mistakes had resulted in more than 30,000 noncitizens being added to voter registration lists across US states since 2000.The latest letter follows a series of actions by the Justice Department targeting state voter registration systems. In July, the department sent letters to election officials in all 50 states warning they could face criminal prosecution if they knowingly allowed noncitizens to remain on voter rolls or cast ballots.