The top US commander in Afghanistan is under investigation for alleged inappropriate communication with a woman whose harassment complaint triggered the resignation of CIA director David Petraeus.
President Barack Obama has delayed General John Allen's nomination as Nato's supreme commander pending a probe by the Pentagon.
The probe came after the FBI handed over 20,000 to 30,000 pages of documents to the Pentagon, most of them e-mails between Allen and Jill Kelley. Kelley is the Florida woman whose complaint to the FBI led to a probe that uncovered an affair between Petraeus and his biographer, Paula Broadwell. Allen denies acting inappropriately.
The shocking revelation came as the FBI searched Broadwell's North Carolina home last night and reports emerged that the agent Kelley initially contacted is under investigation by the internal affairs arm of the FBI after he sent his shirtless photos to her.
Defence Secretary Leon Panetta said Allen would remain commander in Afghanistan while the investigation was under way. But he wanted the Senate to act promptly on General Joseph Dunford's nomination to replace Allen in Afghanistan.
It was unclear how Allen knew Kelley, but he was stationed in Tampa as the deputy director of the US military's Central Command for the three years until he took over in Afghanistan last year. Petraeus was head of Central Command from 2008 to 2010.
But even the sheer volume of communication alone could raise questions. Allen and Kelley were exchanging around 30 pages of communication per day, on average.
A senior defence official said the e-mails were "flirtatious". It wasn't immediately clear whether Allen was flirting or he was the recipient of flirtatious e-mails.
The new details in the case brought expressions of amazement in Congress, already in an uproar over the Petraeus affair. 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."
Evidence that the case involving Petraeus was not fully closed came when FBI agents raided Broadwell's house.
Agents took away what appeared to be two computers and about 10 boxes. The e-mails between Kelley and Broadwell were "childish" and showed some one-upmanship of trying to come across as being more important to Petraeus, one FBI official said.
The agent who is under scrutiny over shirtless photos had never been on the Broadwell case, but had taken the information about the e-mails to the FBI cyber squad in Tampa, a law enforcement official said.
Agence France-Presse, Associated Press, Reuters, Bloomberg