A.I.G. released the names of its major counterparties this month, at the urging of the Federal Reserve Board of Governors. They included Wall Street firms, like Goldman Sachs, JPMorgan Chase and Merrill Lynch, that have successfully resisted efforts to regulate credit derivatives in the past, on the argument that such contracts were valuable risk management tools, safe in the hands of the experts.

In several hearings this month, members of Congress said they believed the derivatives had often been used to speculate, not to manage risk. They have expressed outrage that A.I.G.’s trading partners got 100 cents on the dollar for their money-losing trades when ordinary Americans paying for the bailout have suffered big losses in their 401(k) accounts and other investments.

Some have also been dismayed to learn that taxpayer money had ended up bailing out foreign banks. Some of the biggest beneficiaries of the bailout of A.I.G. were banks in Europe, including Société Générale of France and Deutsche Bank of Germany, each of which received nearly $12 billion, Barclays of Britain, which received $8.5 billion, and UBS of Switzerland, which received $5 billion.

Officials of the Federal Reserve and the Treasury have said they believed A.I.G.’s financial obligations had to be honored to prevent a domino effect. Had A.I.G. suddenly disappeared, banks and other financial institutions around the world would have suffered losses, bad enough in some cases to cause additional failures.

But in their letter, the representatives said that while they were aware of “systemic risk,” they still wanted to know who had decided that the way to contain such risk would be to completely insulate the banks from losses.

“We would like to know if assessments were made of the health and total exposure risks of counterparties, such as Goldman Sachs,” they wrote, pointing out that Goldman Sachs had claimed it had no material exposure to A.I.G., but turned out to have received almost $13 billion during the rescue. “If such assessments were made, by whom were they made and what were the criteria guiding the assessments? Further, was any attempt made to renegotiate and close out these contracts with ‘haircuts?’ If not, why not?”

A person briefed on Mr. Cuomo’s investigation said that A.I.G.’s list of its counterparties gave information only through the end of 2008, and the company was still winding down a vast portfolio of derivatives, including more swaps. He said the attorney general wanted to see whether the termination of the derivatives contracts was being done as efficiently as possible, given the federal resources available to A.I.G.

“Credit-default swap contracts were at the heart of A.I.G.’s meltdown,” Mr. Cuomo said in a statement. “The question is whether the contracts are being wound down properly and efficiently, or whether they have become a vehicle for funneling billions in taxpayers’ dollars to capitalize banks all over the world.”