The adultery scandal that led to the downfall of David Petraeus as CIA director widened Tuesday as President Barack Obama put on hold his nomination of Marine Gen. John Allen as commander of the North Atlantic Treaty Organization, one of the world's top military posts.
The Pentagon said a Federal Bureau of Investigation probe into Mr. Petraeus's communications had revealed that Gen. Allen, now the U.S. commander in Afghanistan, exchanged numerous emails with Jill Kelley, the Florida woman who triggered the investigation. Ms. Kelley had complained to the FBI about receiving harassing emails that the agency later traced to a woman involved with Mr. Petraeus.
On Tuesday, people familiar with the case said that at one point in the summer, after the investigation began pointing to larger potential national security issues, Ms. Kelley tried to get the FBI to drop the matter. The people said she made the request because she was worried about the personal information being provided to investigators.
Ms. Kelley, a 37-year-old volunteer who organized social events for military personnel, developed misgivings after friends in her Tampa social circle urged her to drop the matter, saying the probe would only cause bigger problems, the people familiar with the case said.
Ms. Kelley's apparent regret points to one of the more unusual aspects of the case: what began as a seemingly minor case of cyberstalking mushroomed into fears that the Central Intelligence Agency director's personal email account had been hacked, which spawned concerns the CIA director might have passed sensitive information to his mistress. Each of those fears ultimately proved unfounded, U.S. officials familiar with the probe said. But the investigation eventually exposed Mr. Petraeus's relationship with his biographer, Paula Broadwell, leading to his resignation, according to U.S. officials familiar with the probe.
Into the early fall, investigators focused principally on Ms. Broadwell. They found classified documents on her computer, though they decided there was no proof she had received them from Mr. Petraeus. They also determined that the two had at times shared access to an email account to communicate.
In the course of determining that the email messages Ms. Kelley complained about had been sent by Ms. Broadwell, investigators also discovered reams of emails between Ms. Kelley and Gen. Allen, both of whom are married.
Military officials said the FBI had turned over emails between the two, dating back to 2010. Pentagon investigators haven't found any sensitive or classified material in the messages, though they are still reviewing the material. Another government official said no evidence of criminal wrongdoing or security lapses by Gen. Allen had been found.
Gen. Allen has denied that he had an affair with Ms. Kelley, or that he shared any classified information with her, according to an official familiar with his thinking. He also told officials that he never had been in a room alone with Ms. Kelley and that there had been no affair or sex, the official said.
White House Press Secretary Jay Carney said Mr. Obama remains supportive of Gen. Allen. A defense official urged against prejudging, saying Gen. Allen's nomination as NATO commander may yet go forward. "We probably ought to give him the benefit of the doubt," said a senior defense official.
Ms. Kelley and Ms. Broadwell haven't commented on the scandal. Defense officials said that Gen. Allen was weighing whether to make a statement.
The official familiar with Gen. Allen's thinking described Ms. Kelley as a wealthy socialite who was friendly with many top military commanders in Tampa, home of the U.S. Central Command, which Gen. Petraeus once ran. Though her emails, sent to Gen. Allen and other senior officials, may appear flirtatious in nature, this doesn't mean she engaged in any adulterous relationships, the official familiar with Gen. Allen's thinking said.
This person added that Gen. Allen may innocently have used endearing terms, such as "sweetheart," in his communications with Ms. Kelley.
Defense and military officials who have seen the emails have different opinions of them, said one senior military official. Some see no indication of impropriety while others view them as possibly indicative of an inappropriate relationship. "It is going to come down to your perspective," said one official.
Gen. Allen has told associates he became entangled in the Petraeus adultery scandal a few months ago, when he received an email later traced to Ms. Broadwell, the official familiar with his thinking said.
Ms. Broadwell, whose extramarital affair with Mr. Petraeus had ended by then, believed that Ms. Kelley may have been a romantic rival, according to this official. Besides the emails sent directly to Ms. Kelley, she also sent a flurry of emails from a pseudonymous account to senior military officials, denigrating Ms. Kelley, the official said.
In the email received by Gen. Allen, Ms. Broadwell—writing under the pseudonym KelleyPatrol—described Ms. Kelley as a "seductress" and warned the general about being entangled in a relationship with her, the official said. A lawyer for Ms. Broadwell didn't return messages seeking comment Tuesday.
Gen. Allen was concerned by that email and forwarded it to Ms. Kelley, the official with knowledge of Gen. Allen's thinking said.
FBI agents conducted a consensual search at Ms. Broadwell's home in Charlotte, N.C., Monday, though it was unclear why. Multiple government officials have said that while the FBI doesn't believe Mr. Petraeus committed any crimes, they are still examining Ms. Broadwell's conduct.
Defense Secretary Leon Panetta said that the Pentagon received the information concerning Gen. Allen from the FBI on Sunday.
Some officials believe that if Gen. Allen's account is proved true—that there was no physical relationship and that flirtation was mostly on the part of Ms. Kelley—his nomination to become NATO commander won't be derailed. Gen. Allen will remain commander of the International Security Assistance Force in Afghanistan while the facts are ascertained, Mr. Panetta said.
"His leadership has been instrumental in achieving the significant progress that ISAF, working alongside our Afghan partners, has made in bringing greater security to the Afghan people and in ensuring that Afghanistan never again becomes a safe haven for terrorists," Mr. Panetta said in a statement. "He is entitled to due process in this matter."