Traders being investigated by U.K. regulators for the suspectedrigging of global interest rates are unlikely to face criminalcharges while their firms may suffer record fines, people withknowledge of the probe said.

Britain's Financial Services Authority is scrutinizing evidenceof attempted market abuse as well as failures in banks' systems andcontrols, which carry civil penalties, said the people, whodeclined to be identified because the inquiry is private. To filecriminal charges in England, the regulator would need to showtraders successfully manipulated the rate.

The FSA is among regulators looking into whether banks tried tomanipulate the London interbank offered rate, the benchmark ratefor $360 trillion of securities, to hide their true cost ofborrowing, and whether traders colluded to rig the benchmark toprofit from interest-rate derivatives.