(Reuters) - JPMorgan Chase & Co (JPM.N) has won the dismissal of a nationwide investors' lawsuit accusing the largest U.S. bank of conspiring to drive down silver prices.

U.S. District Judge Robert Patterson in Manhattan said the investors, who bought and sold COMEX silver futures and options contracts, failed to show that JPMorgan manipulated prices at their expense, including by amassing huge short positions that were not justified by market events at the time.

In a decision made public on Monday, Patterson said that while the investors showed that JPMorgan had the ability to influence prices, a fact the bank did not dispute, they failed to show that the bank "intended to cause artificial prices to exist" and acted accordingly.

A lawyer for the investors did not immediately respond to a request for comment.

JPMorgan did not immediately respond to a similar request.

Investors had, in at least 43 complaints filed in 2010 and 2011, accused banks of amassing hundreds of millions of dollars in illegal profit by manipulating silver prices.

After the lawsuits were consolidated, HSBC Holdings Plc (HSBA.L) was dropped in September 2011 as a defendant, leaving JPMorgan and 20 unnamed individuals as defendants.

Patterson had rejected the investors' claims in December, but gave them one last chance to bolster their case.

The complaint had sought triple damages for what it called JPMorgan's antitrust violations in distorting silver prices between 2007 and 2010, including through alleged "fake" trades late in the day when market volume was thin.

The Commodity Futures Trading Commission began probing allegations of silver price manipulation in 2008, and two years later proposed regulations to give it greater power to thwart traders who try to manipulate prices.

The case is In re: Commodity Exchange Inc Silver Futures and Options Trading Litigation, U.S. District Court, Southern District of New York, No. 11-md-02213.

(Reporting by Jonathan Stempel in New York; Editing by Jan Paschal).