WASHINGTON (AP) - The Agriculture Department says a new case of mad cow disease has surfaced in a dairy cow in California.

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The case is the fourth in recent years. John Clifford, the department's chief veterinarian, said the cow from central California did not enter the human food chain and that U.S. meat and dairy supplies are safe.

Clifford did not say when the disease was discovered or exactly where the cow was raised. He said the cow was at a rendering plant in Central California when the case was discovered through U.S.D.A. sample testing.

There have been only three known cases of mad cow disease in the U.S.

Known officially as Bovine Spongiform Encephalopathy, mad cow disease first surfaced in North America in 1993, but the first case in the United States wasn't reported until 2003.

An outbreak of mad cow disease in British cows, however, led to the banning of beef that contained artificial hormones throughout the European Union in the 1990s.

Clifford said the California cow is an atypical case in that it didn't get the disease from eating infected cattle feed.