BEIJING, Feb 6 (Reuters) - An investigation has found nothing amiss at a Chinese food factory, the source of dumplings believed to have made 10 people sick in Japan, state media quoted the joint Chinese-Japanese team as saying on Wednesday.

Both Tokyo and Beijing have called for close cooperation in investigating the case, which has prompted huge Japanese media coverage following a series of health scares over Chinese products ranging from pet food and toys to toothpaste.

"A joint investigation team of China and Japan into the Tianyang Food company has not detected abnormity after a half-day inspection tour in the plant," Xinhua news agency said, quoting a Japanese investigator.

"The plant is very clean and well managed, and no abnormity has been detected. Japan will conduct further analysis based on information and data collected in the plant."

Japan's health minister raised the possibility on Tuesday that someone had deliberately contaminated the dumplings with pesticide.

The mystery is a delicate matter for sensitive Sino-Japanese ties and a domestic headache for Prime Minister Yasuo Fukuda, given criticism from media and opposition lawmakers that it took too long to alert the public.

Chinese Foreign Ministry spokesman Liu Jianchao called on Japan and the Japanese media to look at the issue "calmly, scientifically and responsibly", and not jump to conclusions.

Chinese food quality officials had already said that sample tests on the frozen dumplings, ingredients and packaging at the factory concerned had found no pesticide. Liu added further probes had also not turned up pesticide in samples taken. (Reporting by Nick Macfie; Editing by Sanjeev Miglani)

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