The U.S. commodity futures regulator is looking into claims by a trader in London that JPMorgan Chase & Co. was involved in manipulative silver trading, the Wall Street Journal reported, citing a person close to the situation.

In recent months, U.S. Commodity Futures Trading Commission (CFTC) lawyers have interviewed employees of JPMorgan in its metals trading business, the newspaper said, citing a person familiar with the situation.

Along with JPMorgan, CFTC lawyers have also interviewed industry traders, commodity executives, experts and employees of other metals trading firms, WSJ said.

JPMorgan declined to comment to the Wall Street Journal on any aspect of the investigation. The firm could not immediately be reached for comment by Reuters outside regular U.S. business hours.

On Tuesday, Bart Chilton, a commissioner at the U.S. CFTC said there had been repeated attempts to influence prices in silver markets.

The Journal said JPMorgan and HSBC Holdings have usually been the big players in the silver market.

However, in recent months the banks with large futures positions have sharply reduced the size of their holdings, the paper said.