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The Food and Drug Administration says it will increase testing for the fungicide carbendazim after an unnamed juice company informed the FDA in December that it had detected low levels of the fungicide in its juice and the juice of its competitors.

An FDA spokeswoman said the agency does not believe the fungicide poses a health risk and that the company's testing discovered levels up to 35 parts per billion, significantly under the European Union's maximum level of 200 parts per billion.

The fungicide, which has not been approved for use on oranges in the U.S. but is approved in Brazil, is used to kill and constrain fungi or fungal spores.

"Not all of the orange juice that us consumers drink comes from oranges that were grown here in the U.S.," said Patty Lovera, assistant director of Food & Water Watch. "Just because a chemical is illegal here doesn't mean that other countries don't allow it to be used or that farmers aren't using it there."

According to the U.S. Department of Agriculture, 26.4 percent of orange juice consumed in the U.S. in 2010 was imported, with 56.4 percent of the imports coming from Brazil. The FDA says it will not pull orange juice off store shelves, but will prevent juice that contains traces of the chemical from entering the U.S.

The fungicide fear caused orange juice futures to soar today, with the price of frozen concentrate increasing 10.7 percent to end the day at $2.0775 a pound on the ICE Futures Exchange.

The Associated Press and ABC News' Lisa Stark contributed to this report.