All 10 of the main S&P 500 groups dropped at least 0.5 percent, with energy stocks plunging 3 percent to pace losses. Materials producers sank 1.9 percent even as precious metals rallied. Alcoa Inc. lost 4.7 percent after unofficially starting the earnings season.

The S&P 500 dropped 1.5 percent to 1,939 at 12:54 p.m. in New York, after rallying 1.7 percent yesterday. The Russell 2000 Index dropped 2.2 percent, the most since July. The Dow Jones Industrial Average sank 271.72 points, or 1.6 percent, to 16,722.50, trimming its gain this year to less than 1 percent. Trading in S&P 500 stocks was 29 percent above the 30-day average at this time of day.

“The fear is that global interest rates are so low that there’s risk of deflation, and the economic recovery, which has shown some steady progress, is now deteriorating,” Timothy Ghriskey, who helps oversee $1.5 billion as chief investment officer for Bedford Hills, New York-based Solaris Asset Management LLC, said in a phone interview. “The news out of Europe is nothing new, but it’s come to front and center now with Draghi’s new comments.”