A plunge in U.S. stocks deepened in afternoon trading Wednesday, sending the Dow Jones industrial average down more than 400 points and putting the index on track for its biggest loss in more than a year.

The decline came as investor fears of a global economic slowdown intensified after several weeks of turbulent market action.

The Dow plunged as much as 460 points following steep declines in Europe as investors sized up the latest batch of corporate earnings and some discouraging U.S. economic news. The Dow was heading for its biggest percentage drop since June 2013.

Traders dumped risky assets and parked their money in investments seen as relatively safe, such as U.S. government bonds. That pushed the yield on the 10-year Treasury note briefly below 2 percent, the lowest level in more than a year.

“It’s a function of the U.S. being the best house in a bad neighborhood,” said Terry Sandven, chief equity strategist at U.S. Bank Wealth Management. “There’s still uncertainty about economic growth, primarily on a global basis.”

The Dow recovered some of the ground it had lost in the first half-hour of trading then fell steadily again through the afternoon. By 2:47 p.m. Eastern time it was down 374 points, or 2.3 percent, to 15,941.

The Standard & Poor’s 500 index fell 43 points, or 2.3 percent, to 1,834. The Nasdaq composite dropped 85 points, or 2 percent, to 4,144.

All three indexes are now down for the year.

Bond prices soared as investors shifted money into safe-haven investments.