WASHINGTON, Nov 15: President Obama has seen “no evidence” that US national security was jeopardised in the unfolding scandal between former CIA director David Petraeus and his biographer Paula Broadwell.

“I have no evidence at this point from what I’ve seen that classified information was disclosed that in any way would have had a negative impact on our national security,” President Obama told reporters at his first news conference since winning re-election.

Gen Petraeus, who headed US and Nato forces in Afghanistan before joining the CIA, resigned last week after admitting that he was having an affair with Ms Broadwell.

An FBI investigation, however, has determined that Ms Broadwell had classified materials at her home and on her personal computer.

“Obviously, there’s an ongoing investigation. I don’t want to comment on the specifics of the investigation,” said President Obama when reminded of FBI’s claim. Responding to media reports that the FBI had kept him in the dark, the president said the agency had its own protocols about ongoing investigations and he would ask the FBI director to share those protocols with the public as well.

President Obama praised Gen Petraeus for an “extraordinary career” and for his leadership as a four-star general in Iraq, Afghanistan and at the helm of the CIA.

“From my perspective, at least, he’s provided this country an extraordinary service,” Mr Obama said. “My main hope right now is that he and his family are able to move on and that this ends up being a single side note on what has otherwise been an extraordinary career.”

Explaining why the general offered to resign, the president said: “By his own assessment, he did not meet the standards that he felt were necessary as the director of CIA … and it’s on that basis that I accepted it.”

Meanwhile, the US media reported on Thursday that a single email Ms Broadwell wrote to Mr Petraeus’ successor in Kabul started the process which brought down the CIA director.

Gen John Allen, who replaced Gen Petraeus as the commander of US and Nato forces in Afghanistan, regarded this unsigned message as suspicious and shared it with Jill Kelley, another main character of this scandal.

The email warned him that a friend he planned to meet in Washington the following week “was trouble” and he should stay away from her.

The friend was Jill Kelley, a socialite from Tampa, Florida, who got so annoyed that she asked an FBI agent she knew to investigate.

The agent, who shared shirtless photographs with Ms Kelley, not only investigated the matter but also made it public by sharing it with a lawmaker when his superiors asked him to back off.

Now the two generals and the much decorated FBI agent are all in trouble.

Gen Allen received the first anonymous email in May, under the pseudonym “Kelleypatrol” which ended up at the desk of an FBI agent, Frederick W. Humphries through Ms Kelley. The Florida socialite met the agent at an FBI community programme in 2011.

Although the FBI cut Mr Humphries out of the loop, it continued to investigate and found a substantial number of classified documents on Ms Broadwell’s computer and in her home.

Ms Broadwell has told agents that she took classified documents out of government offices and not from Gen Petraeus. The army has suspended Ms Broadwell’s security clearance, which she had as a former army intelligence officer.