Barclays PLC (NYSE: BCS), Britain's largest publicly owned bank, has suspended six traders, including its chief currency trader in London, as part of an internal investigation into possible currency-market manipulations. None of the traders who were suspended have been formally accused of wrongdoing.

The suspensions, implemented after Britain's Financial Conduct Authority (FCA) began a broad probe into foreign-exchange trading, include Chris Ashton, who runs Barclays' global voice-spot trading operations, the Financial Times said Friday.

A number of major banks have been questioned by regulators, including Royal Bank of Scotland Group PLC (NYSE:RBS), Citigroup Inc. (NYSE:C), Deutsche Bank AG (ADR) (NYSE:DB), UBS AG (U.S. listing) (NYSE:UBS) and JPMorgan Chase & Co. (NYSE:JPM). The global foreign exchange market, worth $3 trillion a day, is run out of London, which accounts for about 40 percent of all trading.

"Various regulatory and enforcement authorities have indicated they are investigating foreign-exchange trading, including possible attempts to manipulate certain benchmark currency exchange rates or engage in other activities that would benefit their trading positions," a Barclays spokesperson said Wednesday.

"The investigations appear to involve multiple market participants in various countries. Barclays Bank has received inquiries from certain of these authorities related to their particular investigations, is reviewing its foreign-exchange trading covering a several-year period through August 2013, and is co-operating with the relevant authorities in their investigations."

Barclays had a brush with regulators last year and was fined for its role in the massive multi-bank Libor (London Interbank Offered Rate) scandal, which has not turned into a criminal investigation by Britain's Serious Fraud Office.