Stocks are closing sharply lower as traders worried about an escalation of tensions between Russia and the West following the downing of a passenger plane in eastern Ukraine.
Traders were also unsettled by poor corporate earnings and a weak indicator for the housing market.
The Dow Jones industrial average fell 161 points, or 0.9 percent, to close at 16,976 Thursday.
The Standard & Poor's 500 index lost 23 points, or 1.2 percent, to 1,958. The Nasdaq lost 62 points, or 1.4 percent, to 4,363.
SanDisk, AutoNation and Mattel were among the biggest decliners after reporting results that disappointed investors.
Prices for gold and U.S. government bonds rose as traders shifted money into assets perceived as being relatively safe.
The yield on the 10-year Treasury note fell to 2.46 percent.
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