PERTH, Australia: The top US commander in Afghanistan, General John Allen, is under investigation for “inappropriate” emails to a woman linked to the sex scandal involving former CIA director David Petraeus, a defense official said on Tuesday.

The revelation represented yet another stunning turn in a widening scandal that has jolted Washington only days after the re-election of President Barack Obama, with lawmakers vowing to get to the bottom of case.

The Pentagon official told reporters that the FBI had uncovered a trove of 20,000 to 30,000 pages of correspondence—mostly emails—between Allen and Jill Kelley, a key figure in the scandal that brought down the CIA chief.

Petraeus—a former four-star general who had previously led the US wars in Iraq and Afghanistan—resigned abruptly last week over an extramarital affair with his biographer Paula Broadwell.

Kelley, a Petraeus family friend, had alerted the FBI earlier this year that she was receiving threatening anonymous emails, which were eventually traced back to Broadwell. The FBI then found emails between Broadwell and Petraeus that revealed their affair.

The senior US defense official, speaking on condition of anonymity, told reporters traveling with Defense Secretary Leon Panetta that there was a “distinct possibility” the Allen emails were connected to the Petraeus investigation.

“The allegations involve inappropriate communications” between Allen and Kelley, the official said.

Panetta said in a statement that his department was informed by the FBI on Sunday about the case and that he had referred it to the Pentagon’s inspector general for investigation.

He said that Allen would remain in Kabul as the commander of NATO-led security forces but that he had asked the Senate Armed Services Committee to delay action on Allen’s pending nomination to be NATO’s supreme allied commander.

Panetta praised the general’s work in Afghanistan, saying that his leadership has been “instrumental” in securing progress in the war against Taliban insurgents.

However, Panetta said that he requested the Senate committee move promptly on the nomination for Allen’s successor in Afghanistan, General Joseph Dunford.

It remained unclear what allegations Allen faced, and officials declined to comment on whether the Marine general was accused of using his work email to communicate with Kelley or had disclosed any classified information.

“It’s far too early to speculate on what the IG [inspector general] might find,” the same defense official said.

“There is enough concern that we believe it was a prudent measure to take appropriate steps to direct an investigation and notify Congress,” he said.

“We need to see where the facts lead in this matter, before jumping to any conclusions whatsoever.”

He added that Allen “disputes that he has engaged in any wrongdoing in this matter.”

Kelley, a 37-year-old Tampa socialite with close military ties, was a family friend of the Petraeuses.

Both Petraeus and Allen served in Tampa, home to US Central Command, which Petraeus led before taking over as commander in Afghanistan in 2010.

On Tuesday the Wall Street Journal reported that the FBI agent initially contacted by Kelley about the threatening emails brought the matter to the attention of Republican lawmakers, believing the bureau was not moving aggressively enough with the investigation.

FBI supervisors had earlier barred the agent from any involvement in the case after he became “obsessed” with the matter, the Journal said.

It quoted one official as saying the agent had sent shirtless photos to Kelley well before the email investigation had begun, and said he is currently under investigation by the internal affairs arm of the FBI.