Plot thickens in sex scandal threatening the nation's security

The sex scandal that has already cost David Petraeus his job as Director of the CIA widened yesterday with confirmation that the Pentagon is investigating "inappropriate communications" between General John Allen, the top US commander in Afghanistan, and a Tampa woman.

The FBI said it had notified the Pentagon on Sunday that General Allen was the source of between 20,000 and 30,000 pages of documents sent, mostly by email, to 37-year-old Jill Kelley, who already has an important supporting role in the slowly unfolding Petraeus drama.

It was Ms Kelley, a volunteer "social organiser" for top brass at the US Central Command in Tampa, who started the chain of events that led to General Petraeus's resignation on Friday when she told the FBI during the summer of threatening emails she had been receiving from an unidentified source. It turned out they were coming from Paula Broadwell, a biographer of General Petraeus with whom he had been having an affair.

The exact nature of the material sent by General Allen to Ms Kelley from 2010 until recently was not known last night and sources close to him insisted that his relationship with her was platonic. However, a Defence Department official said there was concern over "potentially inappropriate" information in the missives while another official spoke to the Associated Press about the use of "flirtatious" language.

While General Allen still had his post last night, Leon Panetta, the US Defence Secretary, asked President Barack Obama to withdraw the nomination of General Allen as the next commander of US European Command. He is due to be replaced as the leader of international forces in Afghanistan by General Joseph Dunford.

Returning from the election recess to Capitol Hill yesterday, members of Congress barely knew what to make of a scandal which reads like an airport pulp novel but which might yet turn out to have serious security implications. "It's a Greek tragedy," Representative Peter King, chairman of the House Committee on Homeland Security, said. "This has the elements of a Hollywood movie."

So far, the plot has been more baffling than titillating. After months of a presidential election that saw nary a jot of nefarious doings, the gods of scandal unleashed a tawdry tale involving two of the country's most revered military figures. Indeed some saw presidential potential in General Patreaus.

At its simplest, it centres on Ms Broadwell who first came to know General Petraeus as the author of his biography. As she gained increasing access to him so a sexual affair blossomed. The FBI stumbled on their extramarital entanglement when it discovered that Ms Broadwell had been the source of the emails to Ms Kelley that were apparently of a "back off from my guy" nature.

General Petraeus has acknowledged the affair, which he said began after he became CIA director in 2010 and was thus no longer a serving general. An adulterous affair is a crime under US military law, which also explains the stakes for General Allen should evidence of a sexual affair between him and Ms Kelley surface.

The FBI is not done yet with the Broadwell connection. On Monday agents went to her North Carolina home and left with boxes of documents and her computer suggesting that the agency wants to be certain that no classified material passed between the former CIA director and the married Ms Broadwell. The Pentagon will be looking to ensure the same is true of the Allen-Kelley chronicles.

Meanwhile new details emerged almost hourly. We have learned, for instance, that the FBI agent who first responded to the request for help from Ms Kelley was swiftly taken off the case because he himself was had been emailing her shirtless pictures of himself. Meanwhile, the New York Post reported both General Petraeus and General Allen had intervened in an especially nasty child custody case on behalf of a twin sister of Ms Kelley.

While Ms Broadwell seized the headlines at the start of the scandal, now Ms Kelley's relationship with messrs Petraeus and Allen is getting more urgent attention. Theirs was a triangle that seemingly began when General Petraeus led Central Command at MacDill Air Force Base in Tampa, near to the home of Ms Kelley, who is married also, prior to taking the Afghanistan command. General Allen was his deputy at MacDill.

The scandal has widening political ramifications. Leaders on Capitol Hill are asking why it took the FBI until the weekend to make public what they had known about General Petraeus and Ms Broadwell since the summer. It upends Mr Obama's reshuffle of his cabinet and top military commanders. And it comes just as General Allen was detailing a final blueprint for drawing down force numbers in Afghanistan.