Raleigh, N.C. — A farm in western North Carolina has been quarantined after a chemical blamed for more than a dozen pet deaths was found in its hogs, state officials said Wednesday. None of the hogs has entered the food supply.

The farm received a shipment of contaminated feed last week, said Mary Ann McBride, assistant state veterinarian for the North Carolina Department of Agriculture and Consumer Services. It was the only farm in the state that received the feed.

"It is important to note that all animals that may have consumed the infected feed have been accounted for," McBride said. "We have no reason to believe that there is any risk associated with the North Carolina pork supply at this time."

State officials took urine samples from 13 hogs, and all tested positive for melamine, a chemical used to manufacture plastics and foam, McBride said. The farm, which wasn't identified, has about 1,400 hogs, she said.

The U.S. Department of Agriculture's Food Safety and Inspection Service has said fewer than 10 hog farms in six states received contaminated feed. The feed came from a Diamond Pet plant in Gaston, S.C., and contained a rice concentrate that has been recalled by its manufacturer in California.

Investigators found melamine in at least two imported Chinese vegetable proteins used to make pet foods. Pet food companies have recalled more than 100 brands of food since the first reports of animal deaths a little over a month ago.

Officials were trying to determine whether hogs in New York, South Carolina, Utah and Ohio also might have eaten the tainted food.

North Carolina is the nation's second-largest hog producer, with 2,300 operating farms. Most are in eastern North Carolina: Duplin and Sampson counties are the largest producers, with more than 2 million hogs each. Bladen County is the third largest, with more than 840,000 hogs.