BEIJING/HONG KONG - China announced a food industry clean-up on Wednesday after exports of a contaminated ingredient in pet food drew global attention.

It will prioritise the inspection of fertiliser and pesticide use in vegetable planting as well as animal medicines and additives in livestock feed, according to a notice from the State Council, China's cabinet.

Beijing has also begun an investigation into the use of melamine scrap, a chemical product that artificially raises the protein level of feed.

The longstanding Chinese practice came under a global spotlight after the death of pets in the United States.

Illustrating the extent of corruption in the regulatory system, Zheng Xiaoyu, a former head of the State Food and Drug Administration, and his former secretary will go to trial on May 15 for taking bribes to approve drugs.

The weak oversight and spate of safety breaches are increasingly raising concern in countries that import food, or food ingredients, from China.

China acknowledged on Tuesday that two Chinese companies illegally exported wheat gluten and rice protein that contained melamine scrap, a chemical product that artificially inflates protein levels. It was mixed into pet food along with another compound, causing a spate of animal deaths in the United States.

The companies denied any wrongdoing.

"There's no such thing. I never ever heard of such a thing. Authorities are investigating this matter," Tian Feng, a Binzhou Futian Biology Technology Co. Ltd. manager, said in a news clip carried on CNN and broadcast in Hong Kong by Cable Television.

Tian was filmed in a detention centre in China speaking to two visitors behind a glass wall.

The other company, Jiangsu-based Xuzhou Anying Biologic Technology Development Company Ltd., earlier denied to Reuters any role in the food contamination case.

"Tests for melamine scrap would be conducted in Jiangsu province first, and then in other areas," said an official with the China Feed Industry Association.

Industry officials said on Wednesday that melamine scrap was unlikely to be linked to an unusually serious outbreak of blue ear disease among pigs in China that started last year.

However, the Ministry of Commerce said draft rules had been issued for pig slaughterhouses, including a ban on the injection of water or other artificial substances to add weight to meat.

REGULATORY WEAKNESS

Experts say China lacks the infrastructure to monitor food quality and safety property, particularly as its exports and trade ties grow.

"China doesn't have a First World regulatory system, and that's its biggest weakness," said a China-based U.S. official.

The official added that there were also weaknesses globally.

A U.S. Food and Agriculture department team has arrived in China to help investigate how melamine got into the feed. It is touring Shandong province, a centre for the poultry and feed industry, and Jiangsu, home to many small chemical producers.

Washington has considered a ban on imports of wheat gluten and rice protein from China, officials have said.

As part of the promised industry clean-up, China will test food, including cooking oil, flour and beverages as well as baby food. Unqualified producers will have their licences revoked, the State Council said in its announcement, dated April 27 but posted on the central government's Web site (www.gov.cn) on Wednesday.

Separately, the Ministry of Health said it would step up hygiene inspections of plants making food from beans.