At 3:24 p.m. Eastern time, the Dow is down 522, or 4.7 percent, at 10,601, a low for the year.
One financial indicator after another shows that investors are losing hope that the economy can keep growing. Thursday's plunge comes a day after the Federal Reserve announced a change in strategy for fighting the economic slowdown.
Economic news was bad around the world. A closely watched survey in Europe indicated a recession could be on the way there, and a manufacturing survey suggested a slowdown in China, which has been one of the hottest economies.