By Matt Jarzemsky

An unnamed firm was reviewing errant stock trades made Tuesday to determine whether it would seek to have them canceled, a spokeswoman for the Financial Industry Regulatory Authority said.

Unusual trades in a number of seemingly unrelated stocks--such as Web radio firm Pandora Media Inc. (P), the U.S.-listed shares of Finnish phone maker Nokia Corp. (NOK) and real-estate investment trust CYS Investments Inc. (CYS)--sparked buzz on trading desks Tuesday. The shares saw brief price spikes up or down before returning to their original ranges.

At least one exchange-traded fund also appeared to be affected. The Financial Select Sector SPDR Fund (XLF), a fund tracking financial shares in the Standard & Poor's 500-stock index, jumped to $16.49 from $16.06 shortly after 10:47 a.m. EST and reverted to the original price seconds later, according to FactSet.

"A firm reported trades to the FINRA/NASDAQ TRF today at prices away from the current market," the FINRA spokeswoman said in an e-mailed statement, referring to a "trade reporting facility," the mechanism used for reporting transactions executed off of an exchange.

Such trading venues, such as "dark pools"--which are privately run stock markets that match up trades electronically--have grown to represent a large share of U.S. equity-market volume.

"The firm is reviewing the trades to determine whether corrections or cancellations of the trades are necessary," the spokeswoman said. She wasn't immediately able to say how many stocks were affected by the mishap and declined to give the name of the firm investigating the trades.

The activity follows a series of technological mishaps and trading errors this year, which critics say have undercut confidence in the U.S. stock market. In August, software problems at Knight Capital Group Inc. (KCG), one of the country's largest facilitators of stock trading, caused erratic trading in dozens of stocks and cost the firm $440 million. Since then, smaller incidents of unusual trading action has afflicted energy stocks and, notably, shares of Kraft Foods Group Inc. (KRFT).

Write to Matt Jarzemsky at matthew.jarzemsky@dowjones.com

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