BROAD SELL-OFF: Most commodity prices fell after the European Central Bank's president offered no immediate measures to support the continent's fragile economy. It came a day after the Federal Reserve ended a meeting without taking new steps to aid the U.S. economy. Slower economic growth means less demand for commodities.

GAS FIZZLE: Natural gas prices plunged nearly 8 percent after the government said stockpiles rose last week. Inventory levels are about 14.5 percent above the five-year average.

WHAT'S NEXT: Traders are awaiting the Labor Department's July employment report, which will be released Friday.