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

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, meanwhile, 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 suffered adverse publicity tied to its notoriously lax enforcement of food and drug safety, but the present round has been especially worrying. China faces criticism from the United States and 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 they would begin testing Chinese seafood for the antibiotics.

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, fertilizers and flame retardants.

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 contaminated with the chemical.

Melamine has no nutritional value but is high in nitrogen. Adding it to feed makes it 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 companies that make food for household pets.

"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 on its Web site.

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 nationwide 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 drug 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.

In Washington, the FDA's commissioner, Dr. Andrew von Eschenbach, and Chinese Ambassador Zhou Wenzhong told two lawmakers Wednesday they would work toward a mutual agreement to improve inspections and the overall safety of food products and drugs traded between the U.S. and China.

That agreement would likely take the form of a memorandum of understanding between the two governments, said Sen. Dick Durbin, D-Ill., who convened the meeting with Rep. Rosa DeLauro, D-Conn.

U.S. officials say they don't believe melamine to be harmful to humans, but say they have too little data to determine how it reacts with other substances.

The FDA says it is particularly concerned about the combination of melamine with cyanuric acid, a similar chemical usually used to help keep swimming pools clean but sometimes used as a feed additive. Some American scientists have suggested that combination may have led to the pet deaths through kidney failure.

Sales managers at four Chinese chemical companies said they were unaware of cyanuric acid's use as a feed additive, although two others said they had heard of the practice but didn't know how widespread it was.

"As far as I know, it is seldom used in animal feed,'' said Chai Zhixian, a salesman with Shanghai Experimental Reagent Co.

The Chinese agency that sets regulator standards for food and drug safety has been in disarray for years. Its director, Zheng Xiaoyu, was dismissed in 2005 and has since been accused of taking up to $780,000 in bribes to approve untested medicines, including an antibiotic that killed at least 10 patients. Zheng is scheduled to go on trial in mid-May, the official Xinhua News Agency said.

The general administration said it checked on 173 exporters in 11 provinces and cities following the FDA's melamine investigation, but found no other signs of tainting after tests on 399 samples, as well as related products, such as processed meats and milk powder.