The F.B.I. told Congress on Sunday that the agency has found no criminality and will not change its conclusions about Hillary Clinton’s use of a private email server as secretary of state.
James B. Comey, the F.B.I. director, said in a letter to members of Congress that “based on our review, we have not changed our conclusions that we expressed in July with respect to Secretary Clinton.”
The news that the bureau was looking at emails that it found on a computer used by a top aide to Mrs. Clinton, Huma Abedin, rocked the presidential race last month and provided a new opening for Donald J. Trump.
Brian Fallon, a spokesman for Mrs. Clinton, said in a post on Twitter that the campaign was always confident that she would be cleared of any wrongdoing.
“We were always confident nothing would cause the July decision to be revisited,” Mr. Fallon said. “Now Director Comey has confirmed it.”
Mr. Comey said in the letter that the bureau has reviewed all communications that were to or from Mrs. Clinton while she was secretary of state since he sent his last letter on Oct. 28.
In July, Mr. Comey said that although Mrs. Clinton and her aides were “extremely careless,” there was no evidence of intentional mishandling of classified information.
In the immediate term, the letter removes a cloud that has hung over the Clinton campaign since Mr. Comey announced his agents were reviewing new emails that might be related to an investigation into Mrs. Clinton that ended in July. But Mr. Comey’s move is sure to raise new questions from Democrats. Most important: Why did Mr. Comey raise the specter of wrongdoing before agents had even read the emails, especially since it took only days to determine they were not significant?
The Clinton campaign welcomed the news.
“We have seen Director Comey’s latest letter to the Hill,” said Jennifer Palmieri, a spokeswoman for the campaign. “We are glad to see he has found — as we were confident he would — that he has confirmed the conclusions he reached in July and we’re glad this matter is resolved.”
At a rally in Minneapolis, Mr. Trump did not directly address Mr. Comey’s letter, but he alluded to it when he said that Mrs. Clinton would be under investigation for a long time. “She’s protected by a rigged system,” he said. “She shouldn’t even be allowed to run for president.”
And Kellyanne Conway, Mr. Trump’s campaign manager, responded to Mr. Fallon in a post on Twitter.
“Then why did you, your colleagues, and your candidate attack Comey and his credibility?” she asked.