Silver bullion is offered for sale at the Chicago Coin Company in Chicago, Ill.
Silver bullion is offered for sale at the Chicago Coin Company in Chicago, Ill. - 
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Jeff Horwich: The Commodities Futures Trading Commission is the Washington agency that's been cracking down on banks for manipulating this interest rate we've been hearing a lot about called LIBOR. Today the Financial Times reports the CFTC may drop another price-fixing investigation it's been working on for years: whether big banks have manipulated the price of silver.

Christopher Werth has more from London.

Christopher Werth: Silver has been a fairly good investment over the past few years. Ben Traynor at the website says five years ago you'd have paid about $10 an an ounce. Today...

Ben Traynor: I'll just double check it. Yeah, it is just below $28.

But some silver investors say the price could be even higher. They accuse big investment banks, such as JP Morgan, of trying to manipulate the market so they could bet on the price of silver dropping. Over the course of the investigation the CFTC it says it's pored over thousands of documents and interviewed dozens of witnesses. But today the Financial Times reports that the agency doesn't have enough evidence to prove a case.

Traynor says those in the metal industry won't be too surprised by the news.

Traynor: Manipulation is a very hard thing to prove. It's very hard to prove if it's happening. It's even harder to prove if it isn't happening.

And many in the industry are doubtful that it is. Nevertheless, Traynor expects suspicions of wrongdoing to continue for a long time to come.

In London, I'm Christopher Werth for Marketplace.