WASHINGTON (Reuters) - Anonymous harassing emails that Tampa socialite Jill Kelley turned over to the FBI contained information about the movements of CIA Director David Petraeus which was not publicly available, a law enforcement source told Reuters.
The fact that the emails' author - later determined to be Petraeus' mistress Paula Broadwell - knew confidential information about the CIA chief's activities was one of the main reasons the FBI felt compelled to launch an in-depth investigation into their origin and motivation, the source said.
The emails, which a second law enforcement source said included warnings to Kelley, a family friend of Petraeus, that the writer knew "what you were doing," were sent to Kelley by a sender who used several fake email addresses.
Disturbed that the anonymous emailer had confidential information about Petraeus' whereabouts, the FBI obtained an administrative subpoena empowering them to examine the email accounts from which the messages were sent to discover the sender's identity, one of the sources said.
Armed with the subpoena, investigators learned that the harassing messages were sent to Kelley by Broadwell, who had written a Petraeus biography. Upon further investigation of Broadwell and her email accounts, investigators discovered additional emails implicating the CIA director and Broadwell in an extra-marital affair, the two sources said.
The sources spoke on condition of anonymity to discuss law enforcement investigations.
Petraeus announced on Friday he was resigning and acknowledged an affair. The scandal this week expanded to include Marine General John Allen, commander of U.S. forces in Afghanistan, whose separate communications with Kelley are now under investigation.
Attempts to reach Broadwell have been unsuccessful, and Petraeus has made no public comment since he resigned.
The law enforcement sources said that as the investigation proceeded, officials sought to determine whether any law or national security regulation had been broken. After interviews were conducted with Broadwell and Petraeus before the U.S. presidential election, investigators tentatively determined that they had no reason to believe Petraeus had broken any law.
The FBI's office in Charlotte, North Carolina, confirmed that on Monday FBI agents visited Broadwell's house, conducting what a law enforcement source described as a search for which Broadwell had granted her consent. Some national security officials have expressed concern, based on Broadwell's public statements and some news reports, that Broadwell may have had access to classified information.
One of the law enforcement sources said that despite the search of Broadwell's house, at this point it still appeared most likely the FBI's investigation related to Broadwell would be closed without criminal charges.
Editing by Warren Strobel and Jackie Frank