NEW YORK — One of the wildest days in stock market history left investors deeply shaken yesterday, with some fearful that another chapter in the global financial crisis was about to unfold.

After sliding through the morning on widening concerns that European governments' debt woes would spread, stocks fell off a cliff late in the day.

The Dow Jones index plummeted more than 700 points in just 15 minutes — and at its low was down nearly 1,000 points — before recouping much of that loss just as quickly.

The speed and depth of the sell-off led many analysts to conclude that trading glitches or errors, compounded by computerized selling, were to blame for the extraordinarily volatile session. But even with its late rebound, the Dow finished down 347.80 points, or 3.2 percent, at 10,520.32.

"Once it gets going it has a mind of its own, like a wild animal," Bill Strazzullo, a veteran trader at Bell Curve Trading in Freehold, N.J., said of automated trading programs.

Among average investors, that could reinforce the impression that Wall Street had created a monster that neither it nor its regulators could control.

The day's extreme decline also immediately revived memories of the market collapse that began in September 2008 after the failure of brokerage Lehman Bros. caused the global financial system to seize up. That fueled the worst economic decline since the Great Depression.

Many analysts agreed that the panicked selling was rooted in the worsening situation in Europe's financial markets, where the crisis of confidence fueled by the Greek government's debt woes has spread to engulf Portugal, Spain and other countries in recent days.

Some experts also pointed to the U.S. Senate vote late Wednesday that would bar future use of taxpayer money to bail out failing financial institutions.

Still, the breathtaking speed of the market's slide yesterday was driven by computerized trading that caused a cascade of automatic selling as the machines took over — reprising not only the worst days of the 2008-09 plunge but also the 22.6 percent crash in the Dow on Oct. 19, 1987, the biggest one-day loss in history.

As traders struggled to explain the day's frantic action, analysts were focusing on the potential fallout.

In recent weeks, as U.S. stocks have largely held up even as Europe's debt crisis has deepened, many analysts have warned that the market was primed for a pullback.

If stocks were to continue to slide, the effect could be to undermine the economic recovery by causing some consumers and companies to pull back from spending.