COLUMBUS, Ohio (AP) — Ohio Treasurer Josh Mandel has asked for a state investigation into whether banks may have manipulated foreign exchange rates charged to Ohio pension funds and the state's injured worker insurance, potentially costing pensioners and businesses tens of millions of dollars over the past 12 years.

In a letter Tuesday requesting that Ohio Attorney General Mike DeWine launch the probe, Mandel said he is concerned that the banks may have engaged in improper currency-trading practices "to maximize the banks' profits, at the expense of Ohio public servants, businesses and taxpayers." State lawmakers have been debating ways to shore up the long-term financial stability of Ohio's pension funds, entertaining proposals that adjust employee and state contributions, trim benefits, and increase retirement ages, among other cost-cutting measures.

Mandel's request comes as a growing number of states are pursuing either investigations or lawsuits against two rival banks that provide foreign investment services to their pensions and other investment funds: State Street Corp. and Bank of New York Mellon Corp. Other states include California, Florida, North Carolina, Virginia and Massachusetts.