The banks are Citibank, BankAmerica, Chase Manhattan, Republic National Bank of New York and the First National Bank of Chicago, a subsidiary of First Chicago Corp.
Douglas Harris, senior deputy comptroller for capital markets at the Treasury's Office of the Comptroller of the Currency, said yesterday that the review had begun a few weeks ago. "We haven't found any big deficiencies yet," he said at the annual meeting of the International Swaps and Derivatives Association in Barcelona.
The Comptroller of the Currency is a member of the Federal Reserve Board, which exercises control over all American national banks. Its report into American exposure to derivatives - financial instruments linked to the underlying value of a share, bond, currency or commodity - is expected in May.
There have been reports that the OCC has been stepping up its vigilance of the fast-moving derivatives market following high-profile losses such as Barings registered in Singapore.
Mr Harris said the five banks being probed were among 25 leading US commercial banks and trust companies that had $15,000bn (£9,500bn) of notional derivatives on their books at the end of 1994. Chemical Bank has the largest: $3,100bn in notional derivatives against assets of $135.7bn.