The U.S. government has expanded a recall of beef to include a total of eight states and the territory of Guam, as a precaution following the discovery of one case of mad cow disease earlier this month.

A cow slaughtered in Washington state on December 9 was found to be infected with Bovine Spongiform Encephalopathy, known as mad cow disease or BSE.

Since the American case was made public last week, U.S. authorities have already recalled more than 4,500 kilograms of beef in the states of Washington, Oregon, California and Nevada.

Department of Agriculture official Kenneth Petersen says investigators have now determined that some of the infected cow's meat may also have gone to Alaska, Hawaii, Idaho, Montana and Guam.

One day earlier, Mr. Petersen stressed that the U.S. government is making the recalls out of, what he called, an abundance of caution, not because it believes there are serious health risks to the public. "We are actively tracking the meat as we speak. But we know that the most highly infectious materials related to BSE are the spinal cord and the brain. And we are certain that those products did not make their way into the food supply," he said.

Mad cow disease is an incurable brain-wasting illness that led farmers in Britain to destroy millions of cattle in the 1980s and 1990s. Humans who eat contaminated beef can contract a rare but deadly variant of the disease.

Chief USDA veterinarian Ron DeHaven said preliminary results show that the infected cow came from a herd in Canada, which had its first official mad cow case in May. "It would appear, based on the information we have today, that the affected animal was very likely to have entered the United States as part of a group of 74 dairy cattle that were imported from the Canadian province of Alberta in August of 2001," he said.

Finding mad cow disease in the United States has huge trade implications. U.S. beef exports last year totalled more than $2.5 billion.

Mr. DeHaven said a high-level U.S. delegation has gone to Asia to meet with officials in Japan and other Asian countries, starting Monday. "They will be providing the Japanese officials and other Asian officials the latest information relative to our investigation, as well as an update on our overall BSE program in the United States," he said.

In Asia, Japan and South Korea were among the biggest importers of U.S. beef, but now are among the more than 20 countries that ban it.

Another big importer, Mexico, said it would lift its ban on U.S. beef as soon as the United States proves that its mad cow case is isolated.