Switzerland's competition watchdog, Weko, has said it is investigating several big banks over the possible manipulation of the precious metals market.
The investigation, which comes after a preliminary probe, will look at possible collusion of bid/ask spreads in the metals market by UBS, Julius Baer, Deutsche Bank, HSBC, Barclays, Morgan Stanley and Mitsui.
"[We have] indications that possible prohibited competitive agreements in the trading of precious metals were agreed among the banks mentioned," Weko said in a statement.
A spokesman added that the probe was likely to be finished by either next year or 2017, and said the banks were suspected of violating Swiss corporate rules.
Some of these banks have already been made to pay out large fines by regulators over their alleged role in the Libor and forex rigging scandals.