On Friday, the department announced it had concluded its investigation into Washington Mutual, the Seattle-based bank that nearly collapsed because of its risky mortgages, without finding evidence of criminal wrongdoing. The Justice Department has also concluded its investigation into Countrywide’s conduct leading into the financial crisis, according to a person with knowledge of that case.

Even more investigations may soon be shut down because the Justice Department is heavily involved in negotiations between big banks and state attorneys general that may give the banks broad immunity against future claims. The state attorneys general are weighing these requests in the mortgage servicing and foreclosure cases, even though the government has not pursued the most basic investigation of these practices.

As it has in similar cases, Bank of America is likely to dispute A.I.G.’s claims in the suit, filed on Monday in New York State Supreme Court. When asked generally about the quality of mortgage bonds issued by companies that are now part of the bank, Lawrence Di Rita, a spokesman for Bank of America, said the disclosures were robust enough for sophisticated investors. He said many of the loans lost value because housing fell.

“Now you have a lot of investors and lawyers who are seeking to recoup the losses from an economic downturn,” Mr. Di Rita said on Sunday, speaking before the bank had seen A.I.G.’s suit.

On Monday morning, after The New York Times had reported A.I.G.’s plans to sue, Mr. Di Rita said in an e-mail: "A.I.G. recklessly chased high yields and profits throughout the mortgage and structured finance markets. A.I.G. is the very definition of an informed, seasoned investor, with losses solely attributable to its own excesses and errors. We reject A.I.G.'s assertions and allegations.”

Mark Herr, a spokesman for A.I.G., responded to Mr. Di Rita's comments by saying: “It is disappointing but unsurprising that Bank of America continues to attempt to blame others for its own misconduct. Investors, no matter how sophisticated, were entitled to rely on its numerous written representations about the securities it sold. Now that it is clear that those representations were false, Bank of America must be held to account.”

Asserting that Bank of America caused A.I.G. billions of dollars in losses, Mr. Herr said, “We are bringing this suit today to protect A.I.G. and the taxpayers' stake in it."