A nationwide inspection of the food-production industry has uncovered the use of a wide range of illegal ingredients in the processing of foodstuffs, the top quality watchdog said Tuesday.

Industrial raw materials, such as dyes, mineral oils, paraffin wax, formaldehyde and the carcinogenic malachite green, have been used in the production of flour, candy, pickles, biscuits, black fungus, melon seeds, bean curd and seafood.

Some processors also use recycled or expired food in their operations, according to the General Administration of Quality Supervision, Inspection and Quarantine.

"These are not isolated cases," Han Yi, director of the administration's quality control and inspection department, said at a press conference.

He said most of the cases involved small, unlicensed food-processing plants employing less than 10 people. All plants caught engaging in illegal practices have been shut down, he added.

Administration figures show that about 75 percent of the 1 million food-processing plants in the country are small and privately owned.

Preliminary figures released yesterday show that since December, when the nationwide inspection was launched, quality inspectors have seized 200 million yuan ($26 million) worth of contaminated or substandard foodstuffs.

At least 180 food plants have been shut down, and 37 had their licenses revoked. Eleven cases have been handed over to judicial organs.

Han said the inspection, which has been focusing on widely consumed foodstuffs, like wine, meat, milk, beverages, soy sauce and cooking oil, is not finished. Rural areas and the suburbs are still considered key areas for inspectors.

Scandals involving substandard food were the subject of many media reports last year. Red-yolk salted duck eggs contaminated with an industrial dye and turbot fish containing carcinogenic residue were two of the more high-profile incidents.

The issue burst into the international spotlight this year after melamine-contaminated wheat gluten and rice protein exported from China tainted pet food in North America.

Han said the administration always puts food safety first and had shown no mercy to violators.

Both the Food Hygiene Law and the Criminal Law ban the use of chemical ingredients or harmful substance in food production. Violators who cause serious poisoning or death face sentences of at least 10 years in jail or even death.

However, Ye Zhihua, a senior researcher of quality standards and testing technology with the Chinese Academy of Agricultural Sciences, worried that the country's many small food plants and inadequate number of enforcement officers could hamper the inspection.

Ye said such small businesses, which usually have poor management and sanitary conditions, are scattered across the country, making supervision difficult.