Law enforcement officials said Tuesday that the FBI was investigating the New York-based insurer for potential fraud, as well as mortgage finance companies Fannie Mae and Freddie Mac, and investment bank Lehman Brothers Holdings Inc.
The four financial institutions' collapse helped trigger the government's $700 billion bailout plan, which continued to be discussed on Capitol Hill Wednesday.
Theand the individuals who ran them, a senior law enforcement official said.
The law enforcement officials spoke on condition of anonymity because the investigations are ongoing and are in the very early stages.
In all, 26 high-profile companies are under intense scrutiny, reports CBS News correspondent Bob Orr.
AIG spokesman Joseph Norton said Wednesday the company did not have details on the FBI investigation, but said "of course we will cooperate with the FBI."
All four companies saw their stock prices plummet this year, as they struggled to survive under the weight of mounting losses tied to bad bets on complex mortgage-related securities.
AIG shares, which lost 71 cents, or 14.2 percent, to $4.29 in afternoon trading Wednesday, traded as high as $70.13 last October, at the beginning of the credit crisis.
Late Tuesday, AIG said it signed a definitive agreement with the Federal Reserve Bank of New York for the deal, which was hammered out last week. A final agreement could be filed as early by end of the week, Norton said.
The agreement provides a two-year, $85 billion emergency loan at an interest rate of about 11.5 percent to AIG, which teetered on the edge of failure because of stresses caused by the collapse of the subprime mortgage market and the credit crunch that ensued.
In return, the government will get a 79.9 percent stake in AIG.
Some of AIG's shareholders had wanted to help the company raise enough money to avoid taking the loan and ceding a majority stake in the company.
The shareholders were considering raising money, which could include bringing in other investors or selling off some of the insurer's assets.
It wasn't immediately clear whether AIG's signing of the agreement ended any of those efforts.
A spokesman for AIG's largest individual shareholder, former CEO Maurice "Hank" Greenberg, said Greenberg supported those efforts, but declined to comment further.
AIG said Tuesday it will repay the government loan in full with proceeds from the sales of some of its assets. It will be up to the company to decide which assets to sell and the timing. The government does, however, have veto power.
Shortly after AIG struck the deal, it announced former Allstate Corp. Chief Executive Officer Edward Liddy was taking over as chairman and chief executive. Liddy replaced Robert Willumstad, who took over the company in June.
"AIG made an exhaustive effort to address its liquidity needs through private sector financing, but was unable to do so in the current environment," Liddy said in a statement Tuesday. "This facility was the company's best alternative. We are pleased to have finalized the terms of the facility, and are already developing a plan to sell assets, repay the facility and emerge as a smaller but profitable company."
He said AIG's insurance subsidiaries remain "strong, liquid and well-capitalized."
AIG operates a range of insurance and financial services businesses ranging from property, casualty, auto and life insurance to annuity and investment services.
The company's problems stem from the more exotic financial products it offers, including some that insure risky debt and bonds against default. The value of those instruments, known as credit default swaps, have deteriorated amid the downturn in the credit markets over the past year.
The swaps are essentially insurance coverage to protect investors against defaulting bonds or debt.