Tests on Chinese-made dumplings suspected of causing a food poisoning outbreak in Japan passed a local inspection, a quarantine chief said on Saturday.

The dumplings were suspected to contain methamidophos. Since 2004, China had banned the use of the pesticide substance on all fruit and vegetable crops.

"Tests showed that material providers Tianyang Food Co. had never used this substance," Cheng Fang, Hebei Provincial Entry-Exit Inspection and Quarantine Bureau director, said at a press conference held in Shijiazhuang, the provincial capital.

At least 10 people in Japan's Hyogo and Chiba prefectures reported stomach ache, vomiting or diarrhoea after eating the dumplings produced by Hebei-based Tianyang Food Co. between Oct. 1 and Oct. 20, according to Japanese media.

"We investigated samples of dumplings which befell the Japanese, as well as dumplings produced within 11 days around Oct. 1 and Oct. 20. No traces of the pesticide had been found," Cheng said.

"We queried 30 workers of Tianyang and the purchasing, manufacturing, storing and transporting processes of the factory without finding any problem in food quality. The factory cooperated well during our investigation," he said.

The company suspended production on Wednesday afternoon and its products were recalled, according to the bureau.

"The factory passed quality control tests in 2001 and 2005," said Di Menglu, Tianyang Food manager, at a press conference held by the factory on Saturday evening. "It (the tests) proved the production accorded with Japanese laws and regulations."

According to Di, the dumplings are put into sealed containers once they come off the production lines. This made it impossible for the dumplings to be contaminated during transport.

In 1994, Tianyang Food Co. obtained from the Chinese government the qualification for producing exported food. Its products are sold only in Japan and not domestically.

Editor: Yan