Following a similar probe from Swiss authorities in early October, the U.K. Financial Conduct Authority (FCA) has opened a formal investigation to determine whether some of the country's banks engaged in a scheme to manipulate foreign exchange rates.

Authorities believe banks from across the globe, including the U.S., pooled information to exchange large sums of money from one currency to another based on markets. According to regulators, one of the main violations is that these banks bought or sold currencies ahead of the 4 p.m. “fix,” which often sees exchange rates fluctuate wildly, without clients' permission in order to turn a profit.

“We are gathering information from a wide range of sources including market participants,” the FCA told Bloomberg in an e-mailed statement. “Our investigations are at an early stage and it will be some time before we conclude whether there has been any misconduct which will lead to enforcement action.”