Justice Department officials pledged to work through the FBI's revived Hillary Clinton email probe "as expeditiously as possible" on Monday amid a backlash over FBI Director James Comey's unexpected public announcement of the investigation on Friday.

"We assure you that the Department will continue to work closely with the FBI and together, dedicate all necessary resources and take appropriate steps as expeditiously as possible," wrote Assistant Attorney General Peter Kadzik in a letter to lawmakers, according to multiple media reports.

The letter came as both Republicans and Democrats in Congress pressed Comey to provide more information about the nature of his bureau's interest in newly-discovered emails found on a laptop used by Huma Abedin, one of Clinton's closest aides. Those emails emerged through a separate investigation of sexual misconduct allegations against Abedin's estranged husband, Anthony Weiner.