A senior manager with a California rendering company said Tuesday a cow at its Hanford, Calif., transfer station tested positive for mad cow disease.
Dennis Luckey, executive vice president of Baker Commodities in Los Angeles, told The Associated Press the disease was discovered after workers selected the cow for random sampling.
The sample was taken from the dead cow's carcass on April 18 at a hide-removal site, he said.
"This animal happened to be one that we randomly selected," Luckey said.
The company does not yet know which farm the cow came from, but the animal never made it to Baker's rendering plant 50 miles away in Kerman, Calif., Luckey said.
On April 19, a lab at the University of California, Davis reported that its test on the sample was inconclusive, he said.
The sample was then sent on to the Agriculture Department, which confirmed on Tuesday that the cow is the fourth discovered in the United States to test positive for the disease.