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 onU.S. stock exchanges saw sudden, big moves on Tuesday beforeresuming normal trading in the latest case of erratic activityin the stock market.

Trades cleared through a Nasdaq-operated trading facilitysparked sharp moves in either direction in a number of seeminglyunrelated stocks, including Pandora Media , Nokiaand the Select Sector Financial SPDR exchange-traded fund.

The trades came through the FINRA/NASDAQ Trade ReportingFacility "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 thatreported the trades, but said the firm is reviewing thosetransactions to determine if cancellations are necessary.

The unusual trades are reminiscent of a technology glitch atKnight Capital Group in early August that generatedrapid price changes and volume spikes, as well as the infamous"flash crash" of May 6, 2010. These and other technologyproblems have heightened concerns that stock markets need moretransparency.

Shares dropped or rose rapidly anywhere from 1 percent tomore than 20 percent between 10:30 a.m. and 11 a.m., withouttriggering any trading halts. Most of the trades were on NewYork Stock Exchange-listed securities.

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

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

While no trade halts were triggered, one stock, MEMCElectronic Materials , had a down-and-up move of about 20percent in less than a second. Two trades in MEMC took place atless 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 anissue. There is chatter along the Street that the exchanges havelost control," said Sal Arnuk, co-manager of trading at ThemisTrading 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 byDavid Gaffen, Clive McKeef, Kenneth Barry, M.D. Golan and AndrewHay)

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