RALEIGH, N.C. — Local veterinarians are investigating a possible case of sick dogs linked to a contaminated brand of pet food.

Eighteen varieties of dog and cat food were removed from store shelves in 22 states last week, including North Carolina, after veterinarians in New York linked the food to 10 dogs' deaths.

The culprit is a naturally occurring toxin called Aflatoxin, which is spawned from mold on corn and causes liver failure.

The North Carolina Department of Agriculture is testing food samples from pet stores across the state. So far, the toxic levels are low, but officials say the bigger challenge may be outside the laboratory.

"A lot of people are returning from vacation and the holiday and they are unaware," said Joe Reardon, of the agriculture department's Food and Drug Protection Division.

As many as seven cases have already been reported in North Carolina. Two cases have also been reported in South Carolina.

The bags of food affected in the recall have a "Best By" date of March 1, 2007 through June 10, 2007.

The problem was detected in the company's Gaston, S.C., distribution center. The Food and Drug Administration is investigating why the problem was not detected before the food left the plant.