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.

"I think that is a weak part of the standards," a food-safety scientist at Consumers Union in Yonkers, Urvashi Rangan, said. An official with an American nonprofit group that certifies Chinese farms as organic, Jeff See, confirmed that testing is not required to get approval to use the logo.

"It's not a regular practice as part of the certification process," Mr. See, the executive director of the Nebraska-based Organic Crop Improvement Association, said. He said he appreciates Americans' concerns that organics from China may not really be organic.

"I understand the questions. It is also a concern for us," Mr. See said. "With China, we've made an extra push here within the last year, even before a lot of this came into public attention. We wanted to make sure what is happening there is represented truly."

A Chinese government report indicates that the organic industry's domestic and export sales more than tripled between 2003 and 2005. About $136 million worth of organic products was shipped overseas in 2005, the report said.

Mr. See said his group has two full-time employees in China who oversee organic certifications for about 250 growers and food processors. The process relies primarily on paperwork audits and on-site inspections looking for unapproved chemicals. All producers are visited at least once a year. "We don't have inspectors in the field 100% of the time," he said. "They do quite a few verification inspections unannounced where they have maybe a day's warning at most. They're pretty thorough."

Some organic advocates doubt whether a yearly inspection, an occasional checkup, and no regular pesticide testing is a regime that ensures the detailed organic rules are being followed, especially in a chaotic, developing country like China. "With the troubles with conventional production over there, there's enough red flags raised" to prompt questions, the author of "Organic Inc.," Samuel Fromartz, said. "It's the Wild West out there."

Produce exposed to pesticides or other toxins can wind up on the market as organic through fraud, error, or environmental contamination, all of which are arguably more likely in the Third World.

China is renowned for counterfeit consumer goods and mislabeled commodities. An industrial chemical mislabeled as wheat gluten, melamine, is believed to have led to a huge recall of tainted pet food earlier this year and the reported deaths of hundreds of animals. In a country where goods ranging from Prada handbags to Duracell batteries are regularly faked, ensuring that a shipment of soybeans came from an organic field and not a chemical-treated one would seem quite a challenge.

"Fraudulent products can be found everywhere in China," an Agriculture Department report on organics noted last year. "Most of the [Chinese] consumers interviewed said they didn't buy and would not buy organic because they don't trust labels or certifications." Still, organic produce typically sells in China for three to five times the price of conventional produce, the report found. That differential increases the incentive for fraud.

In addition, while a farmer in America or Europe can be fairly confident that a fertilizer or pesticide he buys is what it purports to be, even a well-intentioned Chinese farmer cannot be so sure. A weed-killer billed as all natural might be a potent chemical. There are also the problems of groundwater contamination and toxic runoff from neighboring farms. Neither would turn up in a paperwork audit and both might be hard for an inspector to assess without lab testing.

When it issued the organic rules in 2000, the Agriculture Department considered requiring regular testing for pesticides. However, Mr. Fromartz said organic growers from California complained that the tests could show pesticide residues that were the product of drift from nonorganic farms.

" You can't avoid drift," a spokeswoman for California Certified Organic Farmers, Viella Shipley, said. An organic farmer in Santa Cruz, Calif., is suing over pesticide that allegedly traveled in a fog bank after being applied at a neighboring farm, she noted.

The drift issue also could be more serious abroad, where conventional farming can include the use of pesticides not approved by American authorities. The Agriculture Department's rules declare that organic certifiers "may require preharvest or postharvest testing when there is reason to believe that the agricultural input or product has come into contact with a prohibited substance or has been produced using excluded methods." The federal government's testing of produce sold in America, whether imported or domestic, is done by the Food and Drug Administration. In that process, the organic designation is not considered.

"It's not a food safety program. It's a marketing program," an Agriculture Department spokeswoman, Joan Shaffer, said.

An FDA study done in 2003 found that imported produce was about three times as likely to violate limits for pesticide residue. However, it was also more likely than American produce to be free of pesticides altogether. The results suggest that foreign farmers are more likely to use pesticides recklessly, but that many do not use them at all.

Retailers conduct pesticide tests, but they are not forthcoming about the results.

"Based on out own visits and independent tests/audits, we are confident that our vendors in other countries meet if not exceed the standards established for suppliers in the United States," a spokeswoman for Trader Joe's, Alison Mochizuki, said in an e-mail.

A Whole Foods spokeswoman, Ashley Hawkins, said her chain is trying to purchase more produce locally, but cannot get enough. "Our primary challenge at this time is that the demand of fresh fruits and vegetables  especially in organic form  is far outpacing the U.S.-grown supply," she said. "Our team of buyers and auditors personally visit all farms and facilities."

A federal law mandating country-of-origin labeling produce and some meats has been repeatedly delayed, but Trader Joe's and Whole Foods voluntarily label most of their products.

Ms. Anagnoson, the writer, said her surprise over the edamame from China led her to adopt a "China free diet" because of the country's labor and environmental practices. She is even trying to extend the self-imposed ban beyond food to all consumer goods. "When we need to get new laptops, we'll be particularly challenged," she joked.