BEIJING, Dec. 8 (Xinhua) -- Nine Chinese departments will cooperate in a four-month, nationwide investigation to find illegal additives in food.

    The ministries of Health, Industry and Information Technology, Public Security, Supervision, Agriculture and Commerce as well as the State Food and Drug Administration (SFDA), General Administration of Quality Supervision, Inspection and Quarantine (GAQSIQ) and the State Administration for Industry and Commerce (SAIC) will all be involved in the work which starts Wednesday.

    "We plan this action in the wake of the melamine-tainted baby formula," announced Chen Xiaohong, vice minister of health, on Monday.

    Milk powder and other dairy products containing the industry chemical sickened more than 294,000 infants and likely killed six.

    After the scandal broke, authorities began inspecting dairy products but no joint-action of this scale was launched.

    "It was not a single case that banned chemicals were added in foods," Chen said. "We need to address this problem as quickly as possible."

    The investigation will target protein rich foods, such as processed meat, dairy products and sauces, according to Pu Changcheng, deputy director of GAQSIQ.

    Products will be taken from supermarkets and tested to identify any illegal or overused additives.

    The investigation will specifically focus on products made by small food factories as they are often under-supervised and do not have a self-discipline system, Pu said.

    Among China's 500,000 food processing firms, 70 percent are small with less than ten employees, he added.

    In addition, inspectors will work to add newly banned additives to the current quality control list.

    "We will learn a lesson from the baby formula case," Pu said. Previously, melamine was not on the milk powder quality control check list.

    The result of the investigation will be released to the public after it is completed in March.