The mystery of the poisoned pet food continues to unravel as Mao Lijun, head of the Xuzhou Anying Biologic Technology Development Company, has been arrested and is being held “in coastal Jiangsu Province, about 320 miles northwest of Shanghai, though a police spokesman in Pei County declined to say on what charges,” according to the New York Times.

Mao’s company Xuzhau is accused of tainting the wheat gluten with melamine, the substance thought to have killed 16 pets and sickened thousands more. The gluten was routed through a textile company in order to avoid the necessary inspections for items marked for food use. It is thought that the melamine was added as a filler meant to register as protein content when tested, making it appear as if the wheat gluten is of higher quality.

Mao had previously denied any knowledge of how melamine got into the pet food supply, as well as denying that he’d ever exported wheat gluten to the United States. From the New York Times:

ChemNutra, the Las Vegas company that bought the wheat gluten and resold it to pet food makers in the United States, said it thought that Xuzhou was the manufacturer.

Regulators also said that Xuzhou had failed to disclose to China’s export authorities that it was shipping food or feed products to the United States and thereby avoided having its goods checked by food inspectors.

The Xuzhou shipments to ChemNutra were made through another Chinese company, the Suzhou Textiles Silk Light Industrial Company.

Despite its denials of knowing anything about melamine contamination, Xuzhou appears to have sought to buy large supplies of melamine, even in the weeks after the pet food recall.

The company had posted more than a dozen advertisement on the Internet seeking supplies of melamine scrap, the impure waste of an industrial chemical that animal feed producers here often mix into the feed to artificially increase the reading of the protein.

The producers here do that, many acknowledge, to cheat buyers into thinking they are getting higher grade feed, even though the melamine has no nutritional value.

What an %$#$^#.—MEGHANN MARCO

China Makes Arrest in Pet Food Case [NYT]

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