Dozens of Japanese people say they have fallen ill after eating Chinese-made dumplings, prompting Tokyo officials to launch an inquiry.
People said they fell ill and vomited after eating the dumplings
The frozen dumplings, known as gyoza in Japan, were made by Tianyang Food in China's Hebei province.
Japanese officials said they contained traces of pesticide, probably added in production or packaging in China.
China said no traces of pesticide had been found in pre-export inspections, but ordered a halt to production.
The issue has triggered intensive media coverage in Japan and sparked public alarm.
Leaders held an emergency cabinet meeting to discuss the problem.
The problems emerged on Wednesday, when 10 people were reported to have fallen ill from the dumplings - thin dough packets containing ground meat and vegetables which are then fried.
A five-year-old girl was in a serious condition in hospital, reports said.
By late Thursday there were unconfirmed reports of dozens of cases.
The Japanese distributor, JT Foods, has recalled the dumplings and other products made by the same company.
Japan's top government spokesman, Nobutaka Machimura, urged Chinese authorities to investigate.
"I'm afraid there was a rather loose safety awareness on the Chinese side," he said.
Chinese Foreign Ministry spokesman Liu Jianchiao said preliminary tests on two batches of the dumplings had found them to be safe.
"It is not logical to make representations before the results of the investigation are released," he said.
In recent months, Chinese-made products have been involved in several safety scares.
But Japan has also had its problems. Last year, confectioners admitted to mislabelling expiry dates on biscuits and rice cakes.