U.S. Department of Justice prosecutors are investigating at least 10 major banks for allegedly rigging prices in precious metals markets, The Wall Street Journal reported.

Prosecutors from the DOJ's antitrust division are looking into how exactly the prices are set for gold, silver, platinum and palladium in London, while the Commodity Futures Trading Commission (CFTC) is conducting a civil investigation, the newspaper said, citing people close to the inquiries.

The banks being investigated are HSBC Holdings PLC, Bank of Nova Scotia, Barclays PLC, Credit Suisse Group AG, Deutsche Bank AG, Goldman Sachs Group Inc., J.P. Morgan Chase & Co., Société Générale SA, Standard Bank Group Ltd. and UBS AG, according to the Journal.

Investigating authorities made initial requests for information, including a subpoena from the CFTC to HSBC Holdings PLC, according to the bank's annual report released on Monday. The DOJ also requested documents relating to a November antitrust investigation against HSBC.

"This matter is at an early stage and HSBC is cooperating fully," the bank said. "Based on the facts currently known, it is not practicable at this time for HSBC to predict the resolution of these matters."

Since the 2012 Libor interest rate scandal, when 16 of the world's largest banks were sued for manipulating the most common benchmark interest rate, precious metal benchmarks have come under increased regulatory scrutiny, reported Reuters.

In November 2014, Goldman Sachs, Standard Bank, BASF and HSBC were sued in the U.S. in what was called the first nationwide class action suit over price fixing of precious metals, Reuters reported. The plaintiff allegedly lost millions of dollars due to supposed collusion between the banks.

Also in November, Swiss regulators said they found "serious misconduct" by UBS AG employees involved in precious metals price-fixing, calling it a "clear attempt" to manipulate price benchmarks. UBS and five other banks to pay some $4.3 billion in settlements, according to Bloomberg.