UPDATE 2-Erratic U.S. share moves being reviewed-FINRA

(Recasts lead) By Rodrigo Campos

NEW YORK, Oct 9 (Reuters) - A number of issues traded on U.S. stock exchanges saw sudden, big moves on Tuesday before resuming normal trading in the latest case of erratic activity in the stock market.

Trades cleared through a Nasdaq-operated trading facility sparked sharp moves in either direction in a number of seemingly unrelated stocks, including Pandora Media , Nokia and the Select Sector Financial SPDR exchange-traded fund .

The trades came through the FINRA/NASDAQ Trade Reporting Facility "at prices away from the current market," Nancy Condon, a spokeswoman for the Financial Industry Regulatory Authority, said in an email. Condon would not identify the firm that reported the trades, but said the firm is reviewing those transactions to determine if cancellations are necessary.

The unusual trades are reminiscent of a technology glitch at Knight Capital Group in early August that generated rapid price changes and volume spikes, as well as the infamous "flash crash" of May 6, 2010. These and other technology problems have heightened concerns that stock markets need more transparency.

Shares dropped or rose rapidly anywhere from 1 percent to more than 20 percent between 10:30 a.m. and 11 a.m., without triggering any trading halts. Most of the trades were on New York Stock Exchange-listed securities.

The NYSE was looking into the matter, a spokesman said. A Nasdaq spokesman declined to comment.

A source familiar with the matter said Tuesday's odd trades could have been generated in so-called dark pools, trading markets that do not show their order feed publicly.

While no trade halts were triggered, one stock, MEMC Electronic Materials , had a down-and-up move of about 20 percent in less than a second. Two trades in MEMC took place at less than $2 a share when the stock had just been trading at $2.41, according to Thomson Reuters data.

The unusual behavior of the stocks "definitely is raising an issue. There is chatter along the Street that the exchanges have lost control," said Sal Arnuk, co-manager of trading at Themis Trading in Chatham, New Jersey.

Other securities with unusual moves included Las Vegas Sands , Two Harbors Investment and Hatteras Financial .

(Reporting by Rodrigo Campos and Chuck Mikolajczak; editing by David Gaffen, Clive McKeef, Kenneth Barry, M.D. Golan and Andrew Hay)

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