"You don't just suddenly lose $120 billion overnight," said Donn Vickrey of Gradient Analytics, an independent securities research firm in Scottsdale, Ariz.

Mr. Vickrey says he believes AIG must have already accumulated tens of billions of dollars worth of losses by mid-September, when it came close to collapse and received an $85 billion emergency line of credit by the Fed. That loan was later supplemented by a $38 billion lending facility.

But losses on that scale do not show up in the company's financial filings. Instead, AIG replenished its capital by issuing $20 billion in stock and debt in May and reassured investors that it had an ample cushion. It also said that it was making its accounting more precise.

Mr. Vickery and other analysts are examining the company's disclosures for clues that the cushion was threadbare and that company officials knew they had major losses months before the bailout.

Tantalizing support for this argument comes from what appears to have been a behind-the-scenes clash at the company over how to value some of its derivatives contracts. An accountant brought in by the company because of an earlier scandal was pushed to the sidelines on this issue, and the company's outside auditor, PricewaterhouseCoopers, warned of a material weakness months before the government bailout.

The internal auditor resigned and is now in seclusion, according to a former colleague. His account, from a prepared text, was read by Representative Henry A. Waxman, Democrat of California and chairman of the House Committee on Oversight and Government Reform, in a hearing this month.