A broad sell-off in the commodities market continues as the stronger dollar pulls down the price of grains, oil and some metals.

A sharp drop in Chinese stock markets also has commodities investors worrying. A slowdown in China's economy would significantly cut demand for products like copper and oil.

The main focus, however remains the dollar, which is benefiting from a tumbling euro.

The euro, used by 16 countries in Europe, fell to a four-year low against the dollar early Monday. Investors are trying to figure out whether planned budget cuts in countries like Greece, Spain and Portugal will hinder a long-term economic recovery in Europe.

Copper, platinum, palladium and oil are all down more than 2 percent.