Lawyers for investors accusing several major banks of conspiring to rig silver prices are seeking to add 5 new defendants to the case, based on so-called "smoking gun" evidence obtained from Deutsche Bank following a settlement. In papers filed in Manhattan federal court on Wednesday, the lawyers sought to revive previously-dismissed claims against UBS, and add Barclays, BNP Paribas, Standard Chartered and Bank of America as defendants.

Deutsche Bank produced the newly cited evidence after it reached a $38 million settlement in the case earlier this year. The plaintiffs said the evidence showed the new defendants engaged in collusive price manipulation.

In their proposed revised complaint, the investors claim Deutsche Bank, HSBC, Bank of Nova Scotia and others rigged prices of silver and silver financial instruments through a secret daily meeting called the Silver Fix.

The plaintiffs, who are seeking court permission to file the revised complaint, said more than 350,000 pages of documents and 75 audio tapes that Deutsche Bank produced, including electronic chats involving silver traders, backed up their claims.

In October, U.S. District Judge Valerie Caproni dismissed UBS from the case, saying there was nothing showing it manipulated prices, even if it benefited from distortions. But she allowed the investors to file a revised lawsuit against UBS.