Federal prosecutors are investigating foreign-exchange trading at Wells Fargo & Co and have subpoenaed information from the firm, the Wall Street Journal reported, citing people familiar with the matter.

"Wells Fargo learned of an issue associated with a foreign exchange transaction for a single client. The matter was reviewed, the client was promptly notified regarding the issue and Wells Fargo leadership took steps to hold accountable the individuals who were involved," a company spokeswoman said.

The investigation, which is in early stages, is being conducted by the U.S. Attorney's Office for the Northern District of California, the Journal reported.

"Wells Fargo remains committed to its foreign exchange business, meeting its clients' financial needs in an ethical way, and ensuring ongoing review of this and all business operations" the spokeswoman added.