Worries about the U.S. economy are sending the Dow Jones industrial average down 251 points, the second-worst drop this year.
The bad news kept piling up Thursday. Commodity prices slumped in early trading after a report said manufacturing in China fell this month.
The Philadelphia branch of the Federal Reserve also reported a sharp drop in manufacturing in the Northeast.
The Dow closed down 2 percent at 12,574. Alcoa fell the most.
The Standard & Poor's 500 index lost 30 points to 1,326, a decline of 2.2 percent. The Nasdaq fell 71 points, 2.4 percent, to 2,859. All three major indexes lost their gains for the week.
More than four stocks fell for every one that rose on the New York Stock Exchange. Volume was about average, 3.8 billion shares.