FBI agents are at the home of Paula Broadwell, says a spokeswoman (CNN) -- The spiraling scandal that took down former CIA Director David Petraeus has apparently ensnared another powerful general, as authorities announced that Gen. John Allen is under investigation for allegedly sending inappropriate messages to Jill Kelley, a woman who has been linked to the Petraeus scandal. Details of the latest angle of the scandal that has shaken the highest level of the military were sketchy early Tuesday. Some details about Allen, the top U.S. commander in Afghanistan, came from an overnight statement by Defense Secretary Leon Panetta, while he was on his way to Australia. Also President Obama has nominated Gen. Joseph Dunford to succeed Allen in his position at ISAF, and Panetta has urged the Senate to move quickly on the nomination. The investigation into Allen was in its early stages but authorities were looking into some 20,000 to 30,000 pages of documents, the defense official said. Petraeus Probe Could Affect Benghazi Inquiry Days after Petraeus' resignation stunned Washington, investigators were still gathering information about the four-star Army general who once ran the wars in Iraq and Afghanistan. FBI agents were at the Charlotte, North Carolina, home of Petraeus' paramour late Monday, said local FBI spokeswoman Shelley Lynch. She declined to say what the agents were doing at Broadwell's home. Also a video has surfaced of a speech by Broadwell in which she suggested the Libya attack on September 11 was targeting a secret prison at the Benghazi consulate annex, raising unverified concerns about possible security leaks. "I don't know if a lot of you have heard this, but the CIA annex had actually taken a couple of Libyan militia members prisoner and they think that the attack on the consulate was an effort to get these prisoners back," said Broadwell in a speech last month at the University of Denver. Along with questions about Broadwell's access, the Petraeus' scandal also presents challenges to the congressional inquiry into the Benghazi attack. Petraeus recently traveled to Libya to meet the CIA station chief to discuss the attack, CNN has confirmed. The Affair and the e-mails Broadwell and Petraeus first met in 2006 at Harvard University's Kennedy School of Government, where she was a student, Broadwell wrote in the preface of the biography she co-authored on Petraeus. She told him about her interest in studying military leadership, and he offered his help. She traveled to Afghanistan, where she interviewed Petraeus repeatedly. The decision to end the relationship was mutual, the friend said But at some point Broadwell also exchanged e-mails with Kelley. The FBI joined the investigation when Kelley complained that Broadwell was sending harassing e-mails to her in May, a U.S. official told CNN. According to a source with knowledge of the e-mails, the messages accused Kelley of untoward behavior with some generals at MacDill Air Force Base in Tampa, Florida where Kelley did volunteer work. The e-mails detailed the "comings and goings of the generals and Ms. Kelley," said the source, who declined to speak on the record because of sensitivity of the investigation. Among those believed to be referenced in the e-mails was Petreaus. But now it seems that there are more, potentially damaging e-mails, that hold information about Allen, a four-star general who took over as the commander of the war effort in Afghanistan last year. A job he took over from Petreaus. CNN's Joe Sutton, Gloria Borger, Barbara Starr, Suzanne Kelly, Carol Cratty, Candy Crowley, Dana Bash, Pam Benson and Ted Barrett contributed to this report.