About 300 people in Japan's Hyogo and Chiba prefectures sought medical treatment, with one girl in serious condition, in the last week of January after consuming frozen meat dumplings produced by a Chinese factory.

Japanese health officials suspected that the dumpling packages were tainted with a pesticide, methamidophos, and ordered the withdrawal of all frozen and other prepared foods from market shelves thought to have been produced at the Chinese factory. Japan's health minister, Yoichi Masuzoe, told the parliament on January 31 that people complained of severe abdominal pains, vomiting and diarrhoea after eating the dumplings produced by the Hebei-based Tianyang Food Co, which were imported by a Japanese food major Tobacco Inc.

Following the complaints, China's food safety agency carried out tests on the dumplings made by Tianyang Food. On February 2, it said that there was no trace of methamidophos in the food ingredients. China had banned the use of methamidophos on all fruit and vegetable crops since 2004, the agency said.

Chinese officials have now joined Japanese health officials to investigate the incident, suspecting the food was poisoned by miscreants.