"James Comey's surprise announcement that investigators are examining new evidence in the probe of Hillary Clinton's email server put the FBI director back under a harsh spotlight, reigniting criticism of his unusual decision to discuss the high-profile case in front of the media and two congressional committees.

"Comey's former colleagues said his public appearances last summer may have left the director feeling he had no choice but to let the public know when new information possibly relevant to the case arose — in this instance, according to a U.S. official, emails obtained during an investigation into allegations that former Rep. Anthony Weiner (D-N.Y.) exchanged sexually explicit messages with an underage girl.

Some former prosecutors and Justice Department officials said the stir caused by the letter Comey sent Congress Friday announcing the FBI was examining new evidence relevant to the Clinton probe underscored the risks he took when he parted with the usual practice by publicly defending and explaining the FBI's work on the case, even though no charges were filed.

"I got a lot of respect for Jim Comey, but I don't understand this idea of dropping this bombshell which could be a big dud," said former federal prosector Peter Zeidenberg, a veteran of politically sensitive investigations. "Doing it in the last week or 10 days of a presidential election without more information, I don't think that he should because how does it inform a voter? It just invites speculation ... I would question the timing of it. It's not going to get done in a week." Nick Akerman, a former assistant U.S. attorney in the Southern District of New York, was more critical: "Director Comey acted totally inappropriately. He had no business writing to Congress about supposed new emails that neither he nor anyone in the FBI has ever reviewed.”