NEW YORK, Sept 18 (Reuters) - A handful of oil services stocks spiked up in price and trading volume less than 15 minutes before the market's close on Tuesday, but Nasdaq let the trades stand after an investigation by its surveillance team, the exchange said.
After the market's close, Nasdaq said it was investigating potentially erroneous transactions involving seven securities. At 5:15 p.m. the exchange said it had reviewed the transactions and had determined that all trades would stand.
The stocks involved were Diamond Offshore Drilling Inc. , Cameron International Corp, National Oilwell Varco Inc., Tidewater Inc., Exterran Holdings Inc., Ensco Plc and Rowan Cos Plc.
A jump in trading many times over the immediate previous volume occurred in the seven stocks starting at about 3:46 p.m. and stopped within two minutes.
For example, shares of Rowan shot up as much as 7.5 percent to $39.40, with more than 500,000 shares traded, up from less than 15,000 shares that had traded every minute in the prior two hours, data from Thomson Reuters Corp showed.
Nasdaq said its decision could not be appealed.
The spike occurred after prices for the Brent oil contract on Monday plunged nearly $4 in a matter of minutes, possibly because of a single large sell offer in the benchmark contract, brokers and analysts said on Tuesday.