SHANGHAI, China - China vowed yesterday to crack down on contaminated and sometimes deadly food and drugs after a string of sensational revelations about product safety.

The campaign followed an announcement that authorities had detained managers from two companies linked to contaminated pet food that killed dogs and cats in the United States and Canada.

State media said the country's disgraced former top drug regulator would go on trial this month on charges of taking bribes to approve untested medicine.

China has long had a reputation for notoriously lax enforcement of food and drug safety, but the present round of publicity has been especially worrying.

China faces criticism from the United States and the European Union for what they contend are unfair trade practices, and tainted-food scandals could lead to bans on food products that would put hard-pressed Chinese farmers under even greater strain.

Already this year, Mississippi and Alabama have banned catfish from China after tests found ciprofloxacin and enrofloxacin, antibiotics banned for use in the United States. Louisiana officials said Monday that they would begin testing Chinese seafood.

China's government body responsible for overseeing food safety said it had detained an unspecified number of managers from Xuzhou Anying Biologic Technology Development Co. Ltd. and Binzhou Futian Biology Technology Co. Ltd.

That came after the U.S. Food and Drug Administration cited the firms as the source of pet-food ingredients tainted with melamine, a chemical used in plastics and fertilizers.

U.S. inspectors said the tainted gluten was used to make pet food and caused the deaths of an unknown number of dogs and cats, sparking a recall of 154 brands of pet food.

Melamine has no nutritional value, but is high in nitrogen. Adding it makes food appear to be higher in protein, bringing a better price for the makers of feed for stock animals such as pigs, chickens and fish, as well as for pet food.

"Relevant departments will deal strictly with the lawbreaking companies and those responsible according to the results of the investigation," China's General Administration of Quality Supervision, Inspection and Quarantine said online

It said the companies broke regulations by adding the melamine, then broke the law by mislabeling the exported products to avoid inspection.

Calls to the companies were not answered, and police refused to comment. Detention-center phone numbers were not listed.

Separately, the State Council, or Cabinet, said the food-safety crackdown would compel companies to adopt "standards used in food-importing countries . . . and test products which will be used to make animal feed or food for humans."

The government must "strengthen its investigations into protein products, especially melamine," the notice said.

It said all classes of food and drugs would be subject to more rigorous inspections, with an emphasis on securing the food-supply chain and boosting food safety in the vast, mostly impoverished countryside.