The mystery surrounding the poisonous chemical that tainted frozen "gyoza" meat and vegetable dumplings made in China deepened Friday as an extremely high density of the pesticide was detected in remaining samples from a family in the city of Chiba's Inage Ward who fell ill after eating the product.
According to research by Co-op Net, an association of cooperatives, the density of the detected pesticide was 130 parts per million, which is 100 to 400 times higher than Japanese food regulation standards for Chinese chives and cabbage, common ingredients for gyoza.
This high density of methamidophos indicates the chemical did not come from pesticide residue left during the cultivation of the vegetables but was instead added somewhere during the production or distribution process, experts said.