WASHINGTON (AP) -- The sex scandal that led to CIA Director David Petraeus' resignation widened Tuesday, with the top U.S. commander in Afghanistan under investigation for alleged "inappropriate communications" with a woman who received threatening emails from Petraeus' former lover.
A senior defense official told The Associated Press that some of the 20,000-plus pages of documents and emails between Gen. John Allen and Florida socialite Jill Kelley were "flirtatious."
It wasn't immediately clear whether Allen was flirting with Kelley or whether he was the recipient of flirtatious emails. The defense official spoke on condition of anonymity because he wasn't authorized to discuss the case publicly.
Defense Secretary Leon Panetta revealed earlier Tuesday that the Pentagon had begun an internal investigation into the emails.
Allen succeeded Petraeus as the top American commander in Afghanistan in July 2011, and his nomination to become the next commander of the U.S. European Command and the commander of NATO forces in Europe has been put on hold.
In a White House statement early Tuesday, National Security spokesman Tommy Vietor said President Barack Obama has held Allen's nomination at Panetta's request. Obama, the statement said, "remains focused on fully supporting our extraordinary troops and coalition partners in Afghanistan, who Gen. Allen continues to lead as he has so ably done for over a year."
Meanwhile, FBI agents searched the home of Paula Broadwell, the 40-year-old biographer with whom Petraeus had an affair that led to his abrupt resignation Friday.
The resignation and his acknowledgement of an affair stunned Washington because of the former general's highly disciplined and well-praised career, which had led some to speculate whether a run for the White House would be in his future. The 60-year-old retired Army general headed U.S. military operations in Iraq and Afghanistan before taking charge of the CIA.
It was Broadwell's threatening emails to Kelley, a 37-year-old who is a Petraeus family friend, that led to the FBI's discovery of communications between Broadwell and Petraeus indicating they were having an affair.
A Pentagon official earlier Tuesday said 20,000 to 30,000 pages of emails and other documents from Allen's communications with Kelley between 2010 and 2012 were under review. He would not say whether they are thought to include unauthorized disclosures of classified information. He said he did not know whether Petraeus is mentioned in the emails.
Allen has denied wrongdoing. If Allen was found to have had an affair with Kelley, he could face charges of adultery, which is a crime under the Uniform Code of Military Justice.
The new details in the case brought expressions of amazement in Congress, already in an uproar over the Petraeus affair.
Rep. Peter King, chairman of the House Homeland Security Committee, called the case "a Greek tragedy.
"It's just tragic," King said on NBC. "This has the elements in some ways of a Hollywood movie or a trashy novel."
Lawmakers have said they should have been told earlier about the affair and are asking what the FBI knew and when it notified top Obama administration officials.
The White House wasn't informed of the FBI investigation that involved Petraeus until Nov. 6, Election Day, although agents began looking at Petraeus' actions months earlier, sometime during the summer. Senate Intelligence Committee chairwoman Dianne Feinstein said she first learned of the matter from the media late last week and confirmed it in a phone call to the then-CIA director on Friday.
Obama on Friday accepted Petraeus' resignation.
The Justice Department -- of which the FBI is part -- is supposed to refrain from sharing detailed information about its criminal investigations with the White House.
The FBI also looked into whether a separate set of emails between Petraeus and Broadwell might involve any security breach. That will be a key question Wednesday in meetings involving congressional intelligence committee leaders, FBI deputy director Sean Joyce and CIA deputy director Michael Morell.
A federal law enforcement official, speaking on condition of anonymity to discuss details of the investigation, said the FBI had concluded relatively quickly -- and by late summer at the latest -- that there was no security breach. Absent a security breach, it was appropriate not to notify Congress or the White House earlier, this official said.
Extramarital affairs are viewed as particularly risky for intelligence officers, though it is not a crime, because they might be blackmailed to keep the affair quiet.
According to two federal law enforcement officials, the FBI initially began a criminal investigation of unsigned, harassing emails that were sent, beginning last May, to Kelley. She and her husband, Scott, were longtime friends of Petraeus and his wife, Holly. FBI agents traced the alleged cyber harassment to Broadwell and discovered she was exchanging intimate
messages with a private Gmail account. Further investigation revealed that account belonged to Petraeus, under an alias.
Agents later told Petraeus that Broadwell sent emails warning Kelley to stay away from the general and carrying a threatening tone.
Friends and former staff members of Petraeus told The Associated Press that he has assured them his relationship with Kelley was platonic. They said Petraeus was shocked to learn last summer of Broadwell's emails to Kelley.
Petraeus also denied to these associates that he had given Broadwell any sensitive military information.
FBI agents who contacted Petraeus told him that sensitive, possibly classified documents related to Afghanistan were found on her computer, the general's associates said. He assured investigators they did not come from him, and he mused to his associates that they were probably given to her on her reporting trips to Afghanistan by commanders she visited in the field there.
Broadwell had high security clearances as part of her former job as a reserve Army major in military intelligence. But those clearances are only in effect when a soldier is on active duty, which she was not at the time she researched the Petraeus biography.
The FBI concluded there was no security breach.
Nevertheless, the criminal investigation continued into the emails to Kelley, including whether Petraeus had any hand in them. At that point in late summer, FBI Director Robert Mueller and eventually Attorney General Eric Holder were notified that agents had uncovered what appeared to be an extramarital affair involving Petraeus.
Broadwell and Petraeus have each been questioned by FBI agents twice in recent weeks, with both acknowledging the affair in separate interviews. The FBI's most recent interviews with Broadwell and with Petraeus both occurred during the week of Oct. 29, days before the election, one of the law enforcement officials said. The FBI notified Obama's director of national intelligence, James Clapper, of the investigation on Election Day.
In another twist, an FBI agent who was a friend of Kelley and who passed along information from her to the agents who conducted the investigation was subsequently told by his superiors to steer clear of the case because they grew concerned that the agent had become obsessed with the investigation, a federal law enforcement official said. Before the case involving Petraeus got under way, the agent had sent Kelley shirtless photos of himself, according to this official, who spoke on condition of anonymity to discuss the investigation.
Broadwell co-authored a biography titled "All In: The Education of General David Petraeus," published in January. She wrote that she met Petraeus in the spring of 2006 while she was a graduate student at the Kennedy School of Government at Harvard and ended up following him on multiple trips to Afghanistan as part of her research.
Petraeus told one former associate he began an affair with Broadwell a couple of months after he became CIA director in September 2011. They mutually agreed to end the affair four months ago, but they kept in contact because she was still writing a dissertation on his time commanding U.S. troops overseas, the associate said.
Petraeus told former staffers and friends that he had regularly visited the Kelleys' home overlooking Tampa Bay. Kelley served as a sort of social ambassador for U.S. Central Command, hosting parties for the general when Petraeus was commander there from 2008 to 2010.
Kelley regularly kept in touch with Petraeus when he became commander of the Afghanistan war effort, the two exchanging near-daily emails and instant messages, two of his former staffers said. But those messages were exchanged in accounts that his aides monitored as part of their duties and were not romantic in tone, the staffers said.
Petraeus and his family are devastated over the affair -- especially Mrs. Petraeus, who "is not exactly pleased right now" after 38 years of marriage, said Steve Boylan, a friend and former Petraeus spokesman who spoke to him over the weekend.
Broadwell, married with two young sons, has not returned phone calls or emails seeking comment.