No Definitive Word on Potential Trading Error

Updated with latest Citigroup statement, market's opening action.

NEW YORK (TheStreet) -- Trades that occurred in hundreds of stocks at the height of panicked selling on Thursday will be canceled but Procter & Gamble(PG) -- the stock at the center of speculation about a potential trading error -- was absent from the list.

Nasdaq OMX Group(NDAQ), the operator of the Nasdaq Stock Market, released its list of stocks with canceled trades early Friday, while again stating it had no technology or system issues Thursday afternoon. "The NASDAQ Stock Market operated continuously and its close process ran successfully," the company said in a statement.

NYSE Euronext(NYX) is is planning to cancel electronic trades in the same time frame, Katrina Clay, an NYSE Euronext spokeswoman, has told TheStreet.

The Nasdaq's list features the tickers of nearly 300 companies but not shares of P&G, whose brief but precipitous drop was flagged by traders as a potential mistake. Citigroup, which was mentioned on Thursday as possibly being involved with whatever error may have occurred, took a tough stance after looking into the reports.

"As we have said, based on our review, rumors about a trading error by Citi are unfounded," a spokesperson told TheStreet in an e-mailed statement. "It is troubling that inaccurate and unfounded rumors were spread as far as they were."

P&G's stock abruptly fell more than 30% to below $40 from above $60 at around 2:45 PM ET, and the Dow Jones Industrial Average followed by falling more than 600 points in the next 15 minutes, before stabilizing and closing down roughly 350 points amid ongoing fears that Greek's debt crisis would spread to the rest of Europe and possibly trip up the nascent global economic recovery.

The trades being canceled are ones that reflect moves of 60% or more rom the last printed price on a particular issue that occurred between 2:40 PM and 3:00 PM ET on Thursday. P&G didn't experience that extreme of a drop but that's understandable, given the Dow component has a market capitalization of $175 billion and nearly 3 billion outstanding shares. Its momentary plus-30% fall seems harrowing enough. P&G shares closed down less than 3%, however, and a company spokesperson told TheStreet late Thursday that P&G believes the trade below $40 was an "aberration."

Futures were looking higher early Friday as the jobs report came in much stronger than expected but the market was down slightly in recent action, and there was still little clarity about what happened with P&G and the rest of the market during the most dramatic moments on Thursday.

Computer program trading was being widely discussed as a contributing factor in the market's swoon, but it was still unclear to what role such programs, which automatically trigger buy and sell orders when stocks and other trading instruments pass through predetermined levels, played in the action. Earlier Thursday, before the market tanked, the NYSE had issued a press release saying program trading accounted for 23.6% of its average daily volume during the week spanning from April 26-April 30, an average of 717.6 million program trades per day.