A huge influx of orders prevented the New York Stock Exchange from disseminating quotes shortly after the start of trading on Friday.

NYSE Euronext , the parent of the exchange, said the delays followed an inordinate influx of orders received as Friday's session got under way. Later in the session, the company had to temporarily transfer quote processing to a backup system.

The exchange's quote delays caused some tickers to be locked, but an NYSE spokesman said trades are still going through. NYSE's Ray Pellecchia also told Reuters the cause of the problem was still under investigation.

The interruption on the NYSE and in the NYSE Amex cash equities trading was resolved around noon.

Traders who declined to be identified said the interruption was caused in part by the early sell-off as well as by NYSE technology.

These are the problems that we talk about when we talk of systemic risk in the system. When everything is plugged in together, you could easily have systemic issues, said Joe Saluzzi, co-manager of trading at Themis Trading in Chatham, New Jersey.

Ted Weisberg, trader with Seaport Securities in New York, said the disruption had no impact on the market's decline, which steepened after the interruption was resolved. Major stock indexes were down more than 2 percent about 2:30 p.m.

Equities were under pressure Friday, as the S&P 500 index fell 2.5 percent <.SPX> and the Dow industrials <.DJI> lost 2.2 percent, retreating one day after the market's biggest percentage gain in more than three months.

Shares of NYSE Euronext slid 5.4 percent to $26.08 after the NYSE's parent company reported quarterly profits that exceeded estimates, and said it sold a big stake in its U.S. derivatives trading platform.

(Reporting by the Wall Street team in New York; Editing by Kenneth Barry)