The United States has reported its first suspected case of Bovine Spongiform Encephalopathy (mad cow disease) in Washington state.
Agriculture Secretary Ann Veneman said a Holstein cow had tested positive, but she insisted US beef was safe.
Veneman said investigators were trying to find out if any part of the cow had entered the food supply chain.
"We remain confident in the safety of our food supply," she added. "The risk to human health is extremely low."
The suspect cow was tested for BSE on December 9 and a tissue sample was being flown by military jet to Britain for further tests, Veneman said. The first BSE cases were reported in Britain in 1986.
Within hours of the announcement Japan and South Korea said they were temporarily halting beef exports from the US.
The mad cow disease has been linked to a human brain-wasting disease and caused huge losses for the European beef industry in the 1990s.
The only previous outbreak in North America was a single case of BSE at a farm in Alberta, Canada in May.
