JAPAN - Following a Japanese police examination of packs of six frozen gyoza returned from a shop in Hirakata, Osaka Prefecture, police are increasingly of the opinion that the Chinese-made frozen gyoza dumplings were contaminated with a pesticide, methamidophos, in China, according to sources.

Meanwhile, Japan Tobacco Inc., the parent company of Shinagawa Ward, Tokyo-based JT Foods Co., which imported the products, spoke Monday about the operations at the Tianyang Food Processing factory in Hebei Province, China.

"Using a process of elimination we came to the natural conclusion the products were contaminated with the chemical during packaging," a senior Hyogo prefectural police officer said after the police examination into the six returned packs were completed. He said it supported his belief the products were contaminated at the factory in China.

Police did not detect pesticide inside five of the returned six packages of Chuka de Gochiso Hitokuchi Gyoza (delicious Chinese-style bite-sized gyoza), but found the chemical in the dough of the gyoza in one of the packages. However, the gyoza filling in that package did not contain the chemical.

Another police officer said, "[The finding] strengthened our belief that the product was contaminated during the packaging of the products rather than the dumpling production process."

In the two cases in Takasago police did not detect the chemical on the outside of the gyoza packages. In Chiba, the prefectural police found no holes in the packaging. The investigators filled the packages with distilled water to check them for holes.

"We have no choice but to conclude that the packages became tainted with pesticide before they were sealed during the production process," a senior prefectural police officer said.

In the Takasago case, the package had a hole, measuring 1 millimeter by 3 millimeters, leaving open the possibility that the hole was made on purpose by something such as a syringe.

According to JT, the gyoza are prepared for export in two areas.

In the first production stage, conducted on the second floor of a factory building in China, a group of eight to 20 employees chop up ingredients such as pork and vegetables, while the dough is made by another group of between 12 and 18 employees. The ingredients are then wrapped in rolled-out dough by hand by many teams of four people. Dumplings are then cooked and cooled.

At this point as many as 300 employees could have been involved in the process. After that, the gyoza are taken to the first floor for packing. A group of 30 to 50 employees freeze and pack the dumplings before packing them in boxes. Finally, the dumplings, in cardboard boxes, are stored in a freezer. Each operation is conducted by no fewer than four employees during the whole process, according to JT.

The whole process involves more than 330 people, and, as a source close to JT said: "In addition, employees assigned to inspect the operation have access to all parts of the factory. Under such circumstances, how could someone put a chemical inside gyoza packs?"

The package maker resolutely denied it was possible that the frozen gyoza could have been tainted with the chemical before the bagging operation began.

"It's unthinkable. There have been no reported cases of our packaging being punctured during transportation," said the official of Taito Ward, Tokyo-based Totai Co., which asked its subsidiary in Jiangsu Province, China, to produce the packaging for the gyoza products.