INVESTIGATORS are combing Canadian feed mills and rendering plants to try to pinpoint the source of infection for the BSE-infected Washington state cow.

Investigators tentatively traced the first US case of “mad cow disease” to Canada, which could help determine the scope of the outbreak and might even limit the economic damage to the country’s beef industry.

Japan and South Korea banned US beef imports today following an announcement that a recently slaughtered cow had tested for positive for BSE.