The Paper reporter Sun Mingwei

  A trading accident occurred on the New York Stock Exchange (hereinafter referred to as "NYSE"), and about 250 stocks were affected.

  On January 24, local time, many stocks on the New York Stock Exchange showed unusually large fluctuations when the market opened, and some stocks even suspended trading, including some large blue-chip stocks.

Then, around 9:50 a.m., 20 minutes after the opening bell, the NYSE said all of its systems were up and running.

  As of the close, the Dow rose 0.31% to 33733.96 points; the S&P 500 fell 0.07% to 4016.95 points; the Nasdaq fell 0.27% to 11334.27 points.

  A spokesman for the SEC said the agency is investigating the matter.

Some stocks temporarily suspended trading

  Shortly after the opening bell on Tuesday, several stocks on the New York Stock Exchange briefly halted trading due to unusually volatile pre-market trading, Bloomberg reported.

  The stocks hit by the technical glitch included dozens of large companies, in some cases swinging as much as 25 percent between highs and lows in a matter of minutes.

Banks, retailers and industrial stocks including Wells Fargo, McDonald's, Walmart and Morgan Stanley have all been affected.

  Chaos erupted just after the opening bell, according to Bloomberg.

RJ Grant, who handles KBW trading and manages Morgan Stanley's stock, saw eight alerts pop up simultaneously, informing him that the stock had dropped more than 10% in minutes.

While the company hasn't received any large orders for the affected stocks, customers, analysts and salespeople have called to try to figure out what's wrong.

  "It's visually insane, obviously something is wrong with the system," Grant said. "If these stocks open at this price and continue to trade, investors will frantically try to buy stocks that have fallen sharply."

  Many of the affected companies resumed trading by 9:45 a.m., within 15 minutes of the opening bell.

"All NYSE systems are operating normally at this time," the NYSE said 20 minutes after the opening bell, at around 9:50 a.m. ET on Tuesday.

  But the volatility did affect Morgan Stanley's stock price, which closed at $97.13 on Monday and fell to a low of $84.93 on Tuesday before recovering from losses.

Wells Fargo also fell to $38.10 from $45.03 on Monday before bouncing back.

  However, the number of shares trading at unusual market prices is a fraction of the usual stock trading volume, with millions of shares typically changing hands each day.

Thousands of shares in companies including McDonald's and Verizon Communications fell at prices far above or below their last trade.

Shares of other companies, including Nike Inc and Exxon Mobil Corp, have fluctuated by millions of dollars, according to data compiled by Bloomberg.

Some of the initial transactions were declared void

  Initial trades in most U.S. stocks involve a complex but routine process known as the opening auction, designed to limit volatility as orders for the stock pile up before the regular trading session begins.

In it, computers balance supply and demand for a particular stock by establishing an opening price, which can be considered a level that satisfies as many traders as possible.

  But for unknown reasons, some trading varieties did not open for auction on Tuesday. As a result, due to the imbalance between supply and demand, the trading volume of many stocks was very low at the opening, and the opening price was far lower than the closing price on Monday.

  In a subsequent statement, the NYSE referred to a system for U.S. stock trading designed to prevent trading known as limit-up/limit-down (LULD).

When a stock deviates significantly from prevailing prices, the system stops market trading, and the computer makes decisions by keeping a rolling record of average trades over a five-minute period.

At the beginning of a trade, when such an average is not available, the opening price is usually used instead.

  The NYSE canceled some trading in early Tuesday trading, citing its "manifestly erroneous" enforcement rules.

The rule covers "orders executed with manifest errors in any terms, such as price, number of shares and other trading units, or identification of securities."

The exchange is also evaluating flagging some trades as "unusual" trades whose prices will be excluded from the calculation of the day's highs and lows.

  The NYSE did not specify how many stocks were affected.

But the exchange's spreadsheet lists about 250 stocks whose prices are so extreme that they would cancel trades under rules designed to invalidate trades at "manifestly wrong" prices.

Exchange glitches are uncommon

  In fact, it is not common for exchanges to experience technical glitches, but this is not the first time either.

  In July 2015, the NYSE closed trading for nearly four hours due to a technical glitch.

Shortly after the market opened at 9:30 that day, technical problems first arose and initially affected only a small number of stocks.

But later in the morning, the problem resurfaced and affected even more stocks.

At 11:32 am that day, the exchange announced the closure of all transactions.

The New York Stock Exchange did not resume trading until less than an hour before the close.

  The NYSE said at the time that it had decided to close trading to deal with technical issues without any warning to traders on the floor before taking the action.

  In August 2012, Knight Trading, one of the largest market makers at the time, used flawed software that caused erroneous orders to appear on the exchange, causing volatility in the stock market.

The incident drove the company into bankruptcy before it was acquired by a consortium of trading companies.

In May 2022, Citigroup's London trading platform triggered a flash crash, causing stock markets across Europe to plummet.

  A 40-minute blackout in stock trading on three Canadian stock exchanges last November affected some investors, and some refused to place orders even after the exchanges reopened.

Trading on the Toronto Stock Exchange, TSX Venture and Alpha markets was suspended around 10:30 a.m. that day.

and resumed at 11:10 a.m.

All three exchanges, all owned by TMX Group Ltd., halted trading as connectivity issues affected order entry.