HANFORD, Kings County (CBS / AP) — Federal and state agriculture officials are working to find out more about a Central California dairy cow that was found to have mad cow disease.

A spokesman for U.S. Rep. Devin Nunes of California said the sick 5-year-old came from Tulare County, the No. 1 dairy-producing county in the nation.

It’s the first new case of the fatal brain disease in the U.S. since 2006.

The cow died at a dairy and was randomly selected for testing at a transfer facility. A plant official said the cow had exhibited no outward symptoms of the disease.

Agriculture officials say the animal had an atypical form of mad cow, meaning it did not get the disease from eating infected cattle feed.

California health and food officials are assuring consumers that the food supply is safe.

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