Japanese supermarkets, restaurants and schools cleared Chinese food products from their shelves and kitchens Friday in a spiraling nationwide scare over insecticide-tainted dumplings.

The government said at least 10 people have fallen ill since December after eating imported dumplings produced by Tianyang Food Processing. Media reports said the number of victims could be as high as 500.

Heightening the scare, investigators said they found a tiny hole in a dumpling bag recovered from a sickened family, suggesting the food may have been deliberately contaminated, said Kenichi Mizuno, a police official in Hyogo prefecture where three people were hospitalized.

Officials said the insecticide, which is not approved for use in Japan, was found in very high concentrations. One lab test on a leftover dumpling from a sickened family found concentrations at up to 400 times the limit for residues of the insecticide allowed on imported vegetables in Japan, said Co-Op Net, a cooperative that sold the product.

Health Ministry official Rie Hatanaka said the high concentrations were not residue from farm use, though she would not speculate on their source.

Telephone calls to Tianyang and its parent company, Hebei Foodstuffs Import & Export Group, were not answered. Chinese officials have said they stopped the company's production and exports but said tests on pork, cabbage and ginger used in the dumpling batches blamed for the illnesses had shown no sign of the insecticide.

The contamination, which topped Japanese news reports, prompted many stores and restaurant chains to stop using imported Chinese food altogether.

"I'm afraid the dumplings could cause a negative impact on our diplomatic ties," said Foreign Minister Masahiko Komura. "We should promptly take measures to determine the cause and prevent a recurrence before relations are damaged."

Supermarket operators Seiyu Ltd. and Ito-Yokado Co. removed the dumplings and all other products made by Tianyang, while department store Daimaru Inc. removed all food imported from China, the companies said Friday.

The Education Ministry banned Tianyang food products from lunches at the nation's 48,525 schools.

The dumpling scare increased already deep suspicions among consumers in Japan and elsewhere about the safety of Chinese foods. China's exports have come under intense scrutiny in the past year after potentially deadly chemicals were found in goods including toothpaste, toys and seafood.

China's government launched a four-month campaign last August to improve the quality of Chinese products and called it a success.