The closures came amid a nationwide crackdown on shoddy and dangerous products launched in December last year that also uncovered the use of recycled or expired food, the English-language China Daily said.

Formaldehyde, illegal dyes and industrial wax were found in candy, pickles, crackers and seafood, it said.

The report cited Mr Han Yi, an official of the General Administration of Quality Supervision, Inspection and Quarantine, which is responsible for food safety.

'These are not isolated cases,' Mr Han, director of the administration's quality control and inspection department, was quoted as saying.

The official's admission was significant because the administration had said in the past that safety violations were the work of a few rogue operators, a claim which is likely to be part of a strategy to protect China's billions of dollars of food exports.

International concerns over China's food safety problems ballooned this year after high levels of toxins and industrial chemicals were found in exported products.

Chinese-made toothpaste has been rejected by several countries in North and South America and Asia, while Chinese wheat gluten tainted with the chemical melamine was blamed for dog and cat deaths in North America.

Other products turned away by inspectors in the United States include toxic monkfish, frozen eel and juice made with unsafe colour additives.

The authorities in China have pushed for more stringent controls and publicised their efforts to control the problem.

Mr Han said most of the offending manufacturers were small, unlicensed food plants with fewer than 10 employees each, and all had been shut down.

China Daily said 75 per cent of the country's estimated one million food processing plants are small and privately owned.

According to Mr Han, the ongoing inspections focus on commonly consumed food such as meat, milk, beverages, soya sauce and cooking oil.

Rural areas and the suburbs - where standards are likely to be less strict - are still key areas for inspectors, he said.

While the investigation is focused mainly on the countryside, Mr Han said the inspectors intended to go to the cities next.

Meanwhile, another regulatory agency, China's State Administration for Industry and Commerce, said it had closed 152,000 unlicensed food manufacturers and retailers last year for making fake and low-quality products.

It also banned 15,000 tonnes of 'unqualified foods' from entering the market because they had failed to meet national standards.

Its report, posted on the administration's website on Tuesday, highlighted 10 high-profile food scandals, including manufacturers and traders nationwide selling poor-quality edible oil, meat and instant noodles, outdated grain and fake milk and alcohol.

In one case, six people were detained in the northwestern province of Gansu for filling empty bottles of expensive wine with cheaper wine, faking trademarks and then selling them at the price of the original wines, it said.

In north-eastern Jilin province, a grain trader was fined 250,000 yuan (S$50,000) for buying and reselling 41,469 tonnes of outdated grain.

ASSOCIATED PRESS, REUTERS, AGENCE FRANCE-PRESSE