Petraeus Scandal Widens: Gen. Allen Implicated in Affair

from her bone marrow transplant. You need a flow chart to keep track of the sex scandal. It's cost david petraeus his job. And now, overnight, the commanding general of american forces in afghanistan,... See More

from her bone marrow transplant. You need a flow chart to keep track of the sex scandal. It's cost david petraeus his job. And now, overnight, the commanding general of american forces in afghanistan, general john allen, you see him right there. He's implicated, as well. 20,000 to 30,000 pages of e-mails, to jill kelly. The fbi agent you just mentioned has been removed from the case, for sending revealing pictures of himself to that whistleblower. The scandal is growing. And it's resolving around the actions of paula broadwell. One day, more stories leaking out. We'll try to clear it all up for you. Continues to mushroom. Martha raddatz starts out our full coverage from washington. She's been reporting on both generals for a decade. Martha, this was stunning news after midnight. Reporter: It's true. The scandal is more stunning every day. Now, under investigation, the commander who replaced david petraeus in afghanistan, marine corps general john allen, who has apparently been exchanging e-mails with the woman at the center of the petraeus affair. This morning, the fbi probe into david petraeus' affair appears to have also ensnared his successor in afghanistan. The pentagon has now launched an investigation into, quote, potentially inappropriate e-mails between general allen and jill kelly, the petraeus family friend at the center of this increasingly strange scandal. The fbi has turned over 20,000 to 30,000 pages of documents found during the probe. Many are e-mails between allen and kelly sent over the last two years. It was kelly, petraeus' former deputy in tampa, who went to the fbi about threatening e-mails she was receiving. They were eventually traced back to petraeus' biographer, paula broadwell, spurring the investigation that led to the cia director's resignation. Meantime, overnight, nearly a dozen federal agents descended on paula broadwell's home. Spending several hours going floor-to-floor, leaving with a desktop computer, cardboard boxes and a briefcase. Authorities say broadwell consented to the search. Just a few hours later, vernon loeb, who spent 16 months working side-by-side with broadwell on her biography of petraeus, told the website, he had no idea about the affair. There was never a question in my mind. But what was a question in my mind, quite frankly, was why general petraeus was granting paula broadwell the find of access he granted her. Reporter: We are learning more about the scope of the affair between petraeus and broadwell. An official telling abc news, the fbi uncovered hundreds, if not thousands of e-mails between petraeus and broadwell. Many of them salacious in nature. As for the e-mails jill kelly received from broadwell that sent this all in motion, sources tell abc news, references were made to petraeus, but he was not specifically named. Broadwell accused kelly in the e-mails of flaunting herself. Officials tell abc news, kelly told petraeus about the messages. General allen has been nominated to take over nato command, george. But that has now been put on hold. Martha, on hold. Is that a euphemism? Can his career survive this investigation? General allen says he did nothing wrong. But this is likely a career-ender. The investigation will probably take a long time. And they have to fill that job. We're also learning from "the washington post," that general petraeus initially thought he could ride out this storm. Well, perhaps petraeus was hoping it wouldn't become public and he could ride it out because he did not resign until t director of national intelligence told him he should. And president obama held that for 24 hours, as well. Let's go to our senior