Dow Suddenly Drops 1,000 Points On Worries Over Greek Debt, Then Recovers

September 27, 2013 Updated May 6, 2010 at 8:10 PM EDT

By WKBW Programming

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September 27, 2013 Updated May 6, 2010 at 8:10 PM EDT

NEW YORK, NY ( ABC NEWS ) By ALICE GOMSTYN, ZUNAIRA ZAKI, RICH BLAKE and NED POTTER

Stocks took a sudden, breathtaking plungetoday, with the Dow Jones industrial average suddenly falling nearly 1,000 points at one point this afternoon -- before rebounding just as quickly. It closed down some 348 points, at 10,520.32.

David Muir reports on what happened to cause the Dow's biggest single day drop.

More PhotosSources said this afternoon that a trading error at Citigroup may have led to the abrupt drop. The possibility was first reported by CNBC.

The sources told ABC News that the possible error by Citi involved what was supposed to be a $16 million trade on an S&P 500 futures-linked contract. The trade was entered in billions instead, they said.

The trade is believed to have sparked a massive sell-off in shares of Procter & Gamble, because P&G is one of the single largest components of the S&P 500 average. The sell-off was enough briefly to trigger an automatic halt to trading in Procter & Gamble stock.

The brief plunge -- more than 990 points at its low point -- was the biggest intraday point drop in the history of the Dow Jones industrial average. The major averages all closed down more than 3 percent.

ABC News and Nightline will have more on Channel 7.