The Japanese media quoted a senior Chinese food safety official as saying that activists opposed to Chinese government ties with Japan may have contaminated the Chinese-made dumplings that caused 10 people in Japan to fall ill.

The discovery of pesticides on the dumplings has received widespread media coverage in Japan, and has prompted health queries from nearly 4,000 people.

"A small group who do not wish development of Sino-Japanese friendship may have taken extreme measures," Kyodo news agency quoted Wei Chuanzhong, vice minister of the General Administration of Quality Supervision, Inspection and Quarantine. Japan's health minister has also raised the possibility that the food had been deliberately contaminated.