Consumers turning to organic food in the wake of warnings about antifreeze-laden toothpaste, poisoned pet food, and antibiotic-laced fish may be in for a surprise. The same country blamed for those scares, China, is quietly muscling in on the organic market.

Upscale grocery chains like Trader Joe's and Whole Foods now import popular organic snacks such as edamame and canned staples such as kidney beans from China. That has made some buyers looking for pristine, all-natural food a bit skittish.

"A couple of months ago I was just eating some edamame from Trader Joe's because my nutritionist said they were a great source of protein," a science textbook writer from Los Angeles, Stephanie Anagnoson, said. "My husband noticed they were made in China and packed in China, and we both thought that was kind of bizarre. … It was at the same time that everyone began noticing that things coming from China are not necessarily what they seem."

Ms. Anagnoson said she doubts that produce grown in China is truly organic, regardless of the label. "It's really hard to grow something organic in a country that really abuses pesticides and where DDT is used," she said.

Organic produce imported from China carries the U.S. Department of Agriculture's organic logo and is certified by private firms authorized to approve use of the label. However, consumers who view that as a guarantee that the produce is pesticide-free are mistaken. The federal rules establishing the organic certification do not include routine testing for pesticide contamination.