"We are investigating this," Zeng Xing, an official with the General Administration of Quality Supervision, Inspection and Quarantine, told The Associated Press. The administration monitors the export of food, animals and farm products.
It is the first recent high-profile incident of a tainted product being exported. In domestic cases — such as one involving the drug regulators who took bribes to approve shoddy drugs — the government has stepped in and promised investigations.
Xia Wenjun, another administration official, was cited by the state-run Xinhua News Agency as saying that "sampling and examination" of wheat gluten were under way nationwide but did not elaborate.
The probe will center around melamine, Xia said, and the administration will stay in touch with the U.S. Embassy in China. Further measures will be taken "based on developments in the United States," Xia said.
Chinese veterinarians and animal rights activists said they were not aware of any reports of deaths in China due to tainted pet food.
The U.S. Food and Drug Administration has identified a Chinese company in the eastern city of Xuzhou as the supplier of the tainted gluten. The FDA last week blocked wheat gluten imports from Xuzhou Anying Biologic Technology Development Co., saying they contained melamine, a chemical found in plastics and pesticides.
The FDA has confirmed about 15 pet deaths, while anecdotal reports suggest hundreds of cats and dogs may have died of kidney failure from the tainted food.
More than 100 brands of pet foods and treats have been recalled in one of the largest pet food recalls in history, said Stephen Sundlof, director of the FDA's Center for Veterinary Medicine.
Zeng said a report posted to the administration's official newspaper earlier this week led some to believe China denied exporting any wheat gluten to the United States. She said that the administration meant that it had never exported any wheat gluten containing a rat poison, aminopterin.
The New York State Food Laboratory last month identified aminopterin as the likely culprit in the pet food, a finding the FDA later rejected.
Zeng confirmed that China is looking into the claim that it exported wheat gluten containing melamine but declined to give any other details.
The company has also said it is investigating the matter.
Las Vegas-based ChemNutra Inc., which imported the wheat gluten and shipped it to companies that make pet food, said Tuesday that Xuzhou Anying had never reported the presence of melamine in the content analysis it provided.
Earlier this week, Geng Xiujuan, Xuzhou Anying's sales manager, said the gluten was not manufactured by the privately-owned firm, but was bought from companies in neighboring provinces.
Xuzhou Anying produces and exports more than 10,000 tons of wheat gluten a year, according to its Web site. But only 873 tons were linked to tainted U.S. pet food, raising the possibility that more of the contaminated product could still be on the market in China, or abroad.
Mary Peng, a manager of the International Center for Veterinary Services in Beijing, said she's been receiving four to five queries a day from worried pet owners in China asking which food brands are safe. However, there have been no reports of animals sickened by pet food.
"We have not had any reports so far of any animals sickened with these particular symptoms," she said.
Zu Shuxian, an animal rights activist and lecturer at the Anhui Medical University in eastern China, said he also has not heard of any domestic cases.
Melamine is used to make plastic kitchenware, glues, countertops, fabrics, fertilizers and flame retardants. It also is both a contaminant and byproduct of several pesticides, including cyromazine, according to the Environmental Protection Agency.