Story Highlights• Chinese company sold wheat flour containing melamine to pet food distributors
• "I don't even know what this melamine is," detained manager says
• FDA has confirmed deaths of 17 cats and dogs related to pet food recall
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BEIJING, China (CNN) -- The manager of the Chinese company suspected of selling tainted wheat flour to the United States has been detained for nearly two weeks outside Beijing, CNN has learned.
Tian Feng is the manager of Binzhou Futian Biology Technology, which U.S. pet food distributors have identified as the company that sold them wheat flour -- mislabeled as wheat gluten or rice protein concentrate -- containing melamine and related products.
Tian's company was shut by local police on April 25, the day he was detained. (Watch Tian speak to CNN from behind bars )
"I didn't do anything wrong," Tian said in an interview with CNN from the detention center in Binzhou in China's eastern Shandong Province.
Dressed in a white T-shirt and orange prison vest, Tian said, "I don't know about melamine. I don't even know what this melamine is. I have never heard of anyone using it."
Under Chinese law, police can hold Tian for 30 days while the investigation continues. After that, he must be tried or released.
In addition to being used in pet food, the tainted flour also made its way into feed for some 20 million poultry, thousands of hogs, and an unknown number of farmed fish, the Food and Drug Administration said Tuesday.
The FDA has said the threat to humans is remote.
While the FDA has received reports of more than 4,000 pet deaths related to the recall, it has confirmed the deaths of 17 cats and dogs. Agency officials have said they do not plan to investigate the thousands of reports of deaths they have received allegedly caused by the tainted food products.
U.S. food authorities suspect melamine and cyuranic acid -- a chemical used in swimming pools -- were mixed into the flour because the nitrogen-rich compounds would make it appear that the flour contained more protein than it really did.
Researchers say that when melamine is combined with cyuranic acid, crystals can form in the kidneys, leading to organ failure.
Original reports cited tainted rice protein concentrate and wheat gluten as the suspected compounds. But authorities said Tuesday that tests have shown simple wheat flour was the culprit.
Dr. David Acheson, the U.S. Food and Drug Administration's assistant commissioner for food protection, said Tuesday that officials suspect the Chinese company substituted wheat flour for wheat gluten and rice-protein concentrate, then attempted to make them appear to be the protein-rich substances by adulterating them.
Melamine and related compounds each contain high levels of nitrogen. Some tests for protein, which is also rich in nitrogen, test only for the nitrogen.
The Chinese government banned the use of melamine as a food additive only last month.
Cans of recalled pet food fill a shopping cart at a Miami, Florida, pet store in March.