NEW YORK -- Bank of America has revealed that it's received subpoenas and requests for information from various state and federal regulators regarding its sale of auction-rate securities.

In a filing with the Securities and Exchange Commission, the bank said subsidiaries Banc of America Investment Services and Banc of America Securities are cooperating fully with the requests.

Auction-rate securities are bonds whose interest rates are set at periodic auctions, on the basis of bids submitted. The market collapsed in February amid turmoil in the credit markets.

Regulators have been investigating some banks' involvement in the sale of the securities. They claim banks marketed the investments as safe even when they knew of liquidity risks.

Earlier, Citigroup said it reached a settlement with the New York Attorney General and regulators to repurchase $7 billion in auction-rate securities and pay $100 million in fines.