AIG is under a new investigation from New York attorney general Eliot Spitzer.
The company is now facing renewed investigations into its non-traditional products and "certain assumed reinsurance transactions".
A former AIG employee, John Mohs, has pleaded guilty to charges in connection with bid-rigging.
Last week AIG chief executive Hank Greenberg slammed US regulators or strangling the industry with its over zealous approach.
Aon, meanwhile, has put aside $50m (£26m) to settle Spitzer's investigations. But Aon's chief financial officer David Bolger refused to say whether it would be enough.
"It's what we think is the appropriate number at this time, but it could change because we don't have a settlement," he said.
AIG and Aon both said internal investigations had failed to dig up any evidence of fraudulent behaviour.
' AIG reported net income in the fourth quarter of 2004 jumped 11.5% to $3.02bn (£1.6bn), from $2.7bn (£1.6bn) a year earlier.