By DEVLIN BARRETT, EVAN PEREZ and SIOBHAN GORMAN
WASHINGTON—A federal agent who launched the investigation that ultimately led to the resignation of Central Intelligence Agency chief David Petraeus was barred from taking part in the case over the summer due to superiors' concerns that he was personally involved in the case, according to officials familiar with the probe.
After being blocked from the case, the agent continued to press the matter, relaying his concerns to a member of Congress, the officials said.
New details about how the Federal Bureau of Investigation handled the case suggest that even as the bureau delved into Mr. Petraeus's personal life, the agency had to address conduct by its own agent—who allegedly sent shirtless photos of himself to a woman involved in the case prior to the investigation.
FBI officials declined to identify the agent, so he couldn't be reached to give his side of the story. The agent is now under investigation by the Office of Professional Responsibility, the internal-affairs arm of the FBI, according to two officials familiar with the matter.
The revelations address how the investigation first began and ultimately led to Mr. Petraeus's downfall as director of the CIA. The new developments also raise questions about the role played by the FBI and the adequacy of notification to administration and congressional leaders about the scandal.
The FBI agent who started the case was a friend of Jill Kelley, the Tampa woman who received harassing, anonymous emails that led to the probe, according to officials. Ms. Kelley, a volunteer who organizes social events for military personnel in the Tampa area, complained in May about the emails to a friend who is an FBI agent. That agent referred it to a cyber crimes unit, which opened an investigation.
However, supervisors soon became concerned that the initial agent might have grown obsessed with the matter, and prohibited him from any role in the investigation, according to the officials.
One official said the agent in question sent shirtless photos to Ms. Kelley well before the email investigation began, and FBI officials only became aware of them some time later. Eventually, supervisors told the agent he was to have nothing to do with the case, though he never had a formal role in the investigation, the official said.
The agent, after being barred from the case, contacted a member of Congress, Washington Republican David Reichert, because he was concerned senior FBI officials were going to sweep the matter under the rug, the officials said. That information was relayed to top congressional officials, who notified FBI headquarters in Washington.
By that point, FBI agents had determined the harassing emails had been sent by Paula Broadwell, who had written a biography of Mr. Petraeus's military command.
Investigators had also determined that Ms. Broadwell had been having an affair with Mr. Petraeus, and that the emails suggested Ms. Broadwell was suspicious of Ms. Kelley's attention to Mr. Petraeus, officials said.
The accusatory emails, according to officials, were sent anonymously to an account shared by Ms. Kelley and her husband. Ms. Broadwell allegedly used a variety of email addresses to send the harassing messages to Ms. Kelley, officials said.
One asked if Ms. Kelley's husband was aware of her actions, according to officials. In another, the anonymous writer claimed to have watched Ms. Kelley touching "him'' provocatively underneath a table, the officials said.
The message was referring to Mr. Petraeus, but that wasn't clear at the time, officials said. A lawyer for Ms. Kelley didn't respond to messages Monday seeking comment on the anonymous emails or on the alleged emails from the FBI agent. A lawyer for Ms. Broadwell also didn't respond. Neither woman has replied to requests to speak about the matter.
By then, what began as a relatively simple cyberstalking case had ballooned into a national security investigation. Mr. Petraeus and Ms. Broadwell, both of them married, had set up private Gmail accounts to contact each other, according to several officials familiar with the investigation. The FBI at one point was concerned the CIA director's email had been accessed by outsiders.
After agents interviewed Ms. Broadwell, she let them examine her computer, where they found copies of classified documents, according to the officials. Both Mr. Petraeus and Ms. Broadwell denied that he had given her the documents, and FBI officials eventually concluded they had no evidence to suggest otherwise.
Even as the probe of the relationship between Mr. Petraeus and Ms. Broadwell intensified in late summer and early fall, authorities were able to eventually rule out a security breach, though intelligence officials became concerned Mr. Petraeus had left himself exposed to possible blackmail, according to officials.
On Monday night, reporters watching Ms. Broadwell's home in Charlotte, N.C., saw federal agents conduct what appeared to be a search. An FBI spokeswoman confirmed agents were at the home but declined to say what they were doing.
A day after the Nov. 6 election, intelligence officials presented their findings to the White House. Mr. Petraeus met with White House officials last Thursday and announced his resignation the following day.
Lawmakers on Capitol Hill have questioned whether Mr. Petraeus needed to resign over the affair, and some have argued that the FBI should have alerted both the White House and Congress much earlier to the potential security implications surrounding Mr. Petraeus.
In a separate twist in the tangled matter of Mr. Petraeus's resignation, the CIA disputed a theory advanced by Ms. Broadwell that insurgents may have attacked the U.S. consulate and a CIA annex in Benghazi, Libya, on Sept. 11 in a bid to free militants being held there by the agency. Ms. Broadwell suggested that rationale for the consulate attack in an address at the University of Denver on Oct. 26.
"I don't know if a lot of you had heard this, but the CIA annex had actually taken a couple of Libyan militia members prisoner and they think the attack on the consulate was an attempt to get these prisoners back," she said then. "It's still being vetted."
A CIA spokesman said there were no militant prisoners there, noting that President Barack Obama ended CIA authority to hold detainees in 2009. "Any suggestion that the agency is still in the detention business is uninformed and baseless," said the spokesperson.
Some critics pointed to Ms. Broadwell's remarks in Denver as an indication that she may have been passing on classified information, leading to speculation that Mr. Petraeus may have been the source. Based on descriptions by U.S. officials, the romantic relationship had ended by then.
In addition, the source of her comment may not have been intelligence information, but news reports. Earlier in her address, she cited findings of a report that day by Fox News. Immediately after, she mentioned the possibility that the CIA had held militants at the site, which the Fox report also mentioned.
The Sept. 11 consulate attack resulted in the deaths of U.S. Ambassador Christopher Stevens and three other Americans. One person briefed on U.S. intelligence said that reports focused on two main motives for the attack: inspiration from the violent protest that day at the U.S. embassy in Cairo, and the exhortation of al Qaeda leader Ayman al Zawahiri to avenge the death of his second in command. The possibility of attackers trying to free detainees never came up, this person said.
This week, lawmakers are slated to receive a series of closed-door briefings on both Benghazi and the FBI investigation that turned up the affair between Mr. Petraeus and Ms. Broadwell. The Senate Foreign Relations Committee has one such briefing on Benghazi scheduled Tuesday. On Wednesday, leaders of the House intelligence committee—Rep. Michael Rogers, a Michigan Republican who chairs the panel and Rep. C.A. Dutch Ruppersberger of Maryland, the top Democrat—will be briefed by FBI Deputy Director Sean Joyce and acting CIA director Michael Morell.
Senate intelligence committee staffers are working to schedule similar briefings. On Thursday, both the House and Senate intelligence committees were already slated to receive testimony on Benghazi from top intelligence and law-enforcement officials. The investigation that uncovered the affair is now expected to also be a central issue at those hearings, which won't be public.
Sen. Dianne Feinstein (D., Calif.), who chairs the Senate intelligence committee complained Sunday that she and her colleagues should have been told of the Petraeus-Broadwell affair when the FBI discovered it because of national-security concerns.