By Mark Hosenball

WASHINGTON (Reuters) - FBI Director James Comey was driven in part by a fear of leaks from within his agency when he decided to tell Congress the FBI was investigating newly discovered emails related to Hillary Clinton, law enforcement sources said on Thursday.

The examination of the email traffic is now being carried out under the tightest secrecy by a team at Federal Bureau of Investigations headquarters in Washington, the sources said, requesting anonymity because of the inquiry's sensitivity.

Several sources said it was unclear whether the FBI would make any further public disclosures about its latest review before Tuesday's presidential and congressional elections. Two sources said such disclosures were unlikely.

Another source, recently in contact with top investigators, said: "It depends on how it goes and what they find." The source said that, as of Thursday, "nobody really knows" whether the FBI will have anything further to say before the election.

Dropping like a bombshell on the U.S. presidential campaign, Comey's disclosure last Friday in a letter to senior lawmakers just days before the elections raised questions about his motives and drew criticism from some over his timing.

Comey disclosed that the FBI was looking at emails as part of a probe into Clinton's use of a private email system while secretary of state, without describing the emails' content or how long the inquiry might take. The FBI normally does not comment on ongoing inquiries.

The latest emails examination was moving forward "expeditiously," said one source close to the review.

The new emails turned up as FBI investigators were examining electronic devices used by former Democratic Representative Anthony Weiner in connection with an alleged "sexting" scandal. Weiner's estranged wife, Huma Abedin, is a Clinton confidante.

Two law enforcement sources familiar with the FBI's New York Field Office, which initially discovered the emails, said a faction of investigators based in the office is known to be hostile to Hillary Clinton. A spokeswoman for the FBI's New York office said she had no knowledge about this.

Democratic Party sources said such a faction was likely responsible for a recent surge in media leaks on alleged details of an ongoing FBI investigation of the Clinton Foundation.

The FBI has made preliminary inquiries into Clinton Foundation activities and alleged contacts between Trump and associates with parties in Russia, according to law enforcement sources. But these inquiries were shifted into low gear weeks ago because the FBI wanted to avoid any impact on the election.

The FBI previously had spent about a year investigating Clinton's use of the unauthorized server at her home in Chappaqua, New York, instead of the State Department system after classified government secrets were found in some of her emails.

Comey had said in July that while there was "evidence of potential violations of the statutes regarding the handling of classified information, our judgment is that no reasonable prosecutor would bring such a case."

(Editing by Kevin Drawbaugh and Jonathan Oatis)