Feb. 28 (Bloomberg) -- Pesticide-laced dumplings that sickened at least 10 Japanese may have been deliberately poisoned and don't indicate a quality issue with the Chinese producer, China's food-safety agency said.

Investigators examined Tianyang Food Co.'s production process in Hebei province and found no evidence of contamination or substandard ingredients. Tests of the frozen dumplings' packaging found ``little chance'' the pesticide called methamidophos was added in China, the regulator said.

``We conclude that the dumpling-poisoning incident in Japan is an individual contrived case instead of a food-safety case resulting from pesticide residue,'' Wei Chuanzhong, vice minister of China's General Administration of Quality Supervision, Inspection and Quarantine, told the reporters in Beijing today.

Reports of pesticide in dumplings, buns and mackerel have raised concerns among Japanese consumers about the safety of food from China. Japan last year imported 6 trillion yen ($56 billion) of food, excluding livestock, from China.

``There is little chance of putting methamidophos into dumplings in China,'' Wei said. ``The production technique is simple, the process is short. It's almost impossible to bring methamidophos into the workshops.''

Highly Toxic

Methamidophos is a ``highly toxic pesticide,'' according to the Web site of the United Nations' Food and Agriculture Organization.

Tianyang had supplied food to 606 public schools since November, Japan's Chief Cabinet Secretary Nobutaka Machimura said Feb. 5. The school lunches didn't include dumplings and no students have become ill, he said at the time.

Calls to Tianyang have not been returned.

Maruha Corp., Ajinomoto Co. and Japan Tobacco Inc. recalled products supplied by Tianyang last month. Japan Tobacco was forced to scrap a $500 million merger of its frozen food unit with that of Nissin Food Products Co. over the issue.

A mother and her child in Chiba prefecture were hospitalized in December after eating frozen dumplings known as ``gyoza'' in Japan. Health Minister Yoichi Masuzoe last month said food imported from China by Japan Tobacco caused a family of three in western Japan's Hyogo prefecture to become ill.

A family of five in Chiba prefecture, which is east of Tokyo, became sick on Jan. 22.

Police have found traces of the pesticide on six bags of the dumplings seized from a distributor. The police found a hole in one of the packages, according to a Kyodo News report.

Production Halted

Tianyang, located in Shijiazhuang city, southwest of Beijing, is a unit of state-owned Hebei Food Import & Export Group. The company sells frozen and processed meat including wienerwurst, frankfurter sausages, jerky and freeze-dried vegetables. Production at the factory had been halted since Jan. 30, Wei said.

China this month recalled mackerel products exported to Japan, after finding traces of pesticide. Investigators found that the fish was imported from Denmark and the product had been free of chemicals when they left China, Wei said.

Nicky Foods Co., a privately held Japanese company, was reported to have sold meat buns made by its Chinese plant that contained illegal amounts of pesticide. Chinese investigators found no evidence of contamination at Nicky's Renmu Food Co. unit in Shandong province, Wei said. The result was backed up by a Feb. 22 test conducted in Japan, he said.

``Some consumers have become paranoid about China's food,'' he said. ``Even though the mistaken impression has been corrected, it's damaged the reputation of Chinese products.''

To contact the reporter on this story: Eugene Tang in Beijing on eugenetang@bloomberg.net

Last Updated: February 28, 2008 01:26 EST