TOKYO, JAPAN - Japan said Friday that dumplings behind a nationwide scare were likely contaminated with pesticide at a factory near Beijing, as a growing number of consumers shunned Chinese produce.

Thousands of Japanese people have complained of feeling ill after eating dumplings from China, with authorities confirming that 10 of them suffered pesticide poisoning.

Japanese police examining suspicious packages said that the dumplings were properly sealed by the time they were put on sale in Japan.

But he added: "We are not in a position to make the final conclusion as investigators must work cautiously by taking various possibilities into account."

Prime Minister Yasuo Fukuda said separately that the police investigation into the Chinese-made dumplings "has been taking some time, but I think it is getting closer to the heart of the matter."

"We will make our utmost efforts in the investigation so as to restore the system of food safety," Fukuda said in parliament.

Police in western Hyogo prefecture investigated 11 packages of dumplings confiscated after consumers said they looked sticky.

Police found the pesticide methamidophos "on the inner surface and the outer surface of one of the packages. This package did not have any holes until we opened it for investigation," a Hyogo police spokesman told AFP.

China, which is Japan's largest trading partner, has pleaded with Tokyo not to jump to conclusions and said it was investigating the cause of the pesticide scare.

A Japanese government team this week said it found nothing unusual when it toured the factory of Tianyang Food Company near Beijing that produced the frozen dumplings for a unit of Japan Tobacco Inc..

Officials in both countries have raised the possibility of deliberate tampering with the dumplings, although their governments have made more cautious statements.

With businesses closed for the week-long Lunar New Year holiday in China, phone calls to Tianyang Food Company went unanswered on Friday.

Attempts to call China's General Administration of Quality Supervision, Inspection and Quarantine were also unsuccessful.

Despite the ongoing investigation, the scare has taken a toll on Japanese consumption of Chinese produce.

China, whose soaring economy relies on its status as a manufacturing hub, is the second biggest food supplier to Japan after the United States.

Daiei Inc., one of Japan's major supermarket chains, said its sales of frozen food, much of it made in China, has dropped by 30 percent from a year earlier since the news of the poisoned dumplings emerged last week.

"Instead, sales of produce with which to cook dumplings yourself are rising," a Daiei spokesman said.

Sales of domestic onions, pork and beef have all gone up by more than 150 percent, he said.

Ito Yokado, another supermarket operator, set up a special space in its stores for people looking to make dumplings themselves.

"This has been really popular," said a Ito Yokado spokesman. "We hear a lot of customers voicing fear over Chinese-made frozen foods, although we don't have statistics."

Japan, the world's second largest economy, imports 60 percent of its food, giving it the lowest self-sufficiency rate among the Group of Seven rich nations.