Updated at 3:08 p.m.

The rollercoaster ride on Wall Street continued Wednesday, as U.S. stock market indices fell again on worries about the weakening economy.

The Dow Jones Industrial Average plunged 520 points, or 4.6 percent, to 10,719. The S&P 500 and Nasdaq each closed down more than 4 percent.

The Dow gave back much of its gain from Tuesday, when it surged 429 points after the Federal Reserve pledged to keep its key interest rate at nearly zero into 2013.

But the Fed’s statement also included a dim outlook on the economy. It said growth has been “considerably slower” than it expected and that it anticipates a slower pace of recovery.

Job market expands

On Tuesday, the Labor Department reported that the number of available jobs rose to 3.1 million in June, up from 3 million in May. It was the highest total since March, and a sign that hiring could improve a bit in the coming months.

Roughly 4.5 unemployed people, on average, were competing for each available job in June. That’s down slightly from 4.6 in May.  In a healthy economy, the ratio is about 2 to 1.

Wholesale sales, inventories up

Wholesale companies added to their stockpiles of autos, machinery and computers in June. Inventories rose for the 18th consecutive month and sales rebounded after a May decline.

The Commerce Department says wholesale inventories increased 0.6 percent in June after a 1.7 percent gain in May.

Sales at the wholesale level rose 0.6 percent in June. That followed a 0.3 percent drop in May. Sales have risen in 10 of the past 12 months.

Stockpiles at the wholesale level have risen to $458.7 billion, up 19.6 percent from the low point hit in September 2009. Rising demand could convince businesses to keep restocking their shelves, which could boost growth at a critical time when the economy has slowed.