Worries about a possible trade war helped send stock prices down sharply Thursday, with the Dow Jones industrial average losing nearly 3 percent of its value.
The Dow finished at 23,598, a decline of 724 points. The drop left both the Dow and the Standard and Poor's 500 index in negative territory for the year.
The plunge in prices came on the same day that President Trump was announcing tens of billions of dollars in tariffs on Chinese imports. Beijing has threatened to retaliate with tariffs of its own.
Among the big losers were Boeing and Caterpillar, both of which depend heavily on the export market. Both lost more than 5 percent of their value.
The drop sent investors scurrying to safe investments, and bond prices rose.
The financial markets have been especially volatile lately, for reasons that go beyond fears about trade.
Facebook, which has been dealing with fallout over its handling of user data, has been losing ground all week, and that has sent shares of other technology companies falling.