--Shares of Rowan Cos. and other oil- and gas-related stocks see brief price spikes in late-afternoon trading

--Exchanges let trades stand after investigating them

--Activity follows high-profile glitches in trading this year

 
   By Matt Jarzemsky 
 

Seven oil- and gas-related stocks saw brief price spikes in the closing minutes of U.S. trading Tuesday, the latest sign of unusual activity that has unnerved some market participants.

Around 3:47 p.m. EDT, shares jumped between 3% and 9% in oil- and gas-equipment makers National Oilwell Varco Inc. (NOV), Cameron International Corp. (CAM), Exterran Holdings Inc. (EXH); offshore drillers Rowan Cos. (RDC), Ensco PLC (ESV) and Diamond Offshore Drilling Inc. (DO); and Tidewater Inc. (TDW), a provider of marine services to the oil and gas industry.

All of the affected stocks quickly reversed those gains, and each closed within 2% of the prices at which they began the day.

The activity led to an investigation by exchange operators such as Nasdaq OMX Group (NDAQ), NYSE Euronext (NYSE) and Direct Edge Holdings LLC, which sent advisories to traders noting the unusual activity was "potentially erroneous." The exchanges later said trades in the affected stocks would stand.

Spokesmen for NYSE and Nasdaq declined to comment. A Direct Edge spokesman couldn't immediately be reached.

The unusual price action comes as exchanges brace for greater scrutiny from the Securities and Exchange Commission, which announced Friday it had fined NYSE Euronext as part of a settlement involving allegations of improper delivery of market data. NYSE Euronext didn't admit or deny the allegations.

Earlier this year, trades caused by faulty software at Knight Capital Group Inc. (KCG) led to a $440 million loss for the firm.

In the wake of that episode and other tech-related glitches--such as the failed listing of BATS Global Markets this spring and problems with Facebook Inc.'s (FB) initial public offering in May--the SEC scheduled a roundtable on market technology issues for Oct. 2.

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

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