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.”

Bloomberg says the London-based FCA is conducting the investigation, “alongside a number of other agencies both in the U.K. and abroad into a number of firms.” On Oct. 7, European Union regulators said they were reviewing the foreign exchange market as well for any irregularities.

When the FCA originally began reviewing the allegations, two of the banks specifically named were the German Deutsche Bank AG and the American Citigroup Inc. The Royal Bank of Scotland Group Plc has also confirmed that it is cooperating with the FCA in the investigation.

On Sept. 25, U.S. and U.K. authorities announced that they were fining brokerage firm ICAP $90 million for its role in manipulating benchmark interest rates, notably the London interbank offered rate (LIBOR). Because of the scope of the allegations here, however — $5.3 trillion is traded daily on the foreign exchange market — penalties for any wrongdoing could be much higher.