"Instead of sheer accidents, most of the recent stomach-turning food safety incidents are a consequence of intentional violations of food safety regulations and processing procedures," said Yu Jun, a senior official with the Food Safety Commission under the State Council, China's Cabinet, at the Third China Food Safety Forum.

"Cases include incidents caused by additives, such as melamine, clenbuterol and the steamed buns colored with chemicals found in Shanghai and Zhejiang province," Mr Jun said.

Clenbuterol, an additive that makes pigs leaner but causes health problems in humans, stirred another widespread fear of pork safety in the country in recent months. China's largest meat processor, the Shuanghui Group, apologized in April for selling pork products that contained the additive.

More recently, the disease control authority in Hangzhou, capital of Zhejiang province, said it found that products of a local company contain plasticizer used to soften plastic.

"In addition to physical, chemical and biological pollution that caused food safety incidents, the contamination of violators' integrity is more salient," said Wang Hong, deputy director of the department of food production supervision under the General Administration of Quality Supervision, Inspection and Quarantine.

"In the past, food safety issues in China were caused by sanitation problems, such as microbiological and environmental pollution. Now the situation has changed. The lust for profits stimulates some food producers to break the law," Mr Jun said.

Food safety experts said a well-rounded legal framework and a reliable and powerful law enforcement agency is badly needed.

"Shady food producers will only adventure into the game of risk and return when they know the chance of being investigated and treated is very small," said Peter Ben Embarek, food safety and nutrition technology officer of the World Health Organization's China Office.

To address the existing problems, the Chinese government will continue to carry out a variety of supervision and investigation campaigns on food safety, officials said.