A cow slaughtered in Washington state earlier this month had tested positive for BSE, better known as mad cow disease, Agriculture Department officials announced yesterday. The discovery marks the first time the dreaded illness has been detected in the United States.

Meat from the infected animal traveled through three separate processing plants before a test revealed the problem 13 days later. Japan, the largest foreign customer for U.S. beef, announced a temporary halt to U.S. beef imports. South Korea, Singapore, Thailand, Malaysia, Taiwan, Hong Kong and Russia have also barred beef imports.