US Agriculture officials confirmed Monday that a cow in Alabama has tested positive for mad cow disease.
Results were confirmed by more detailed testing at a government laboratory, and more tests are being done this week.
Officials are not saying where they found the cow but they do say it had not entered the food supply for people or animals.
US Investigators have found two previous cases of mad cow disease.
The first was in December 2003 in a Canadian-born cow in Washington State. The second was last June in a cow that was born and raised in Texas.