WASHINGTON — James B. Comey, the F.B.I. director, faced a dilemma on Thursday when deputies briefed him about the discovery of a trove of emails that might be linked to the inquiry into Hillary Clinton’s private email server that was closed months ago.

Mr. Comey could immediately inform Congress about the emails, which were found in an investigation into former Representative Anthony D. Weiner. That unusual step, months after Mr. Comey had cleared Mrs. Clinton of any criminal wrongdoing in the email case, would risk accusations that he was unfairly harming her presidential campaign less than two weeks before the election.

Or he could delay any announcement and examine the new emails more closely, risking criticism that he had suppressed important new information if it came out after the election, despite his pledges of “transparency” in the investigation.

Mr. Comey, a Republican appointed by President Obama three years ago, decided that he could live with criticism of his judgment, aides said. So on Friday morning, the F.B.I.’s congressional liaison emailed a letter from the director to the chairmen and ranking members of eight congressional committees — virtually ensuring that it would be quickly publicized by eager Republicans.