WASHINGTON — The FBI investigation that led to the resignation of David H. Petraeus as CIA director Friday began with a complaint several months ago about ‘‘harassing’’ emails sent by Paula Broadwell, Petraeus’ biographer, to an unidentified third person, a government official briefed on the case said Saturday.
When FBI agents following up on the complaint began to examine Broadwell’s emails, they discovered exchanges between her and Petraeus that revealed that they were having an affair, said the official, who spoke of the investigation on the condition of anonymity.
The person who complained about harassing messages from Broadwell, according to the official, was not a family member or a government official. One congressional official who was briefed on the matter Friday said senior intelligence officials had explained that the FBI investigation ‘‘started with two women.’’
''It didn’t start with Petraeus, but in the course of the investigation they stumbled across him,’’ said the congressional official, who said the intelligence officials had provided no other information about the two women or the focus of the inquiry. ‘‘We were stunned.’’
Petraeus said in a statement that he was resigning after 14 months as head of the Central Intelligence Agency because he had shown ‘‘extremely poor judgment’’ in engaging in the affair after 37 years of marriage.
The government official dismissed a range of media speculation that the FBI inquiry might have focused on leaks of classified information to the press or even foreign spying. ‘‘People think that because it’s the CIA director, it must involve bigger issues,’’ the official said. ‘‘Think of a small circle of people who know each other.’’
The FBI investigators were not pursuing evidence of Petraeus’ marital infidelity, which would not be a criminal matter, the official said. But their examination of his emails, most or all of them sent from a personal account and not from his CIA account, raised the possibility of security breaches that needed to be addressed directly with him.
‘'Alarms went off on larger security issues,’’ the official said. As a result, FBI agents spoke with the CIA director about two weeks ago, and he learned in the discussion, if he was not already aware, that they knew of his affair with Broadwell, the official said.
Web-based email like Gmail and Yahoo Mail can be quite vulnerable to hacking, and it is possible that FBI experts were studying whether Petraeus’ accounts had been compromised. Any possibility that hackers could use the CIA director’s email as a route to break into sensitive government computer systems would be an obvious concern.
But the fears of bigger security problems proved unjustified, and the security questions were resolved, the official said.
Neither the congressional intelligence committees nor the White House learned of the investigation or the link to Petraeus until this week, officials said. Some congressional staff members said they believed the bureau should have informed at least the Republican and Democratic leaders of the House and Senate intelligence committees about the unfolding inquiry, and the committees are likely to demand an explanation of why they were not told.
White House officials said they were informed Wednesday night that Petraeus was considering resigning because of an extramarital affair.On Thursday morning, just before a staff meeting at the White House, President Barack Obama was told.That afternoon, Petraeus went to see him and informed him that he strongly believed he had to resign. Obama did not accept his resignation right away, but on Friday, he called Petraeus and accepted the resignation.
‘'Dave’s decision to step down represents the loss of one of our nation’s most respected public servants,’’ James R. Clapper Jr., the director of national intelligence, said in a statement Friday.
A senior intelligence official said Saturday that Clapper had learned of Petraeus’ situation only when the FBI notified him about 5 p.m. Tuesday.That night and the next day, the official said, the two men discussed the situation, and Clapper told Petraeus ‘‘that he thought the right thing to do would be to resign,’’ the intelligence official said.
Clapper notified the president’s senior national security staff late Wednesday that Petraeus was considering resigning because of an extramarital affair, the official said.