Fears surrounding the safety of the U.S. beef supply abated somewhat after a pair of cows suspected of Mad Cow disease were both found to be clear of the disease. Concern spread when the Agriculture Department received “inconclusive” preliminary screenings on the animals, indicating possible Mad Cow disease. Even at the time of the preliminary screenings, however, officials cautioned that the tests are so sensitive that the results did not necessarily mean additional cases had been discovered.

In fact, federal officials were quick to note that the rapid screening tests are extremely sensitive and, in themselves, do not confirm the presence of the disease. Nonetheless, the “inconclusive” result was the first such determination in more than 8,500 tests. Authorities did not disclose the location of either animal, its state of origin or the facility where it was killed or tested. However, more conclusive tests were conducted at the department's National Veterinary Services Laboratories in Ames, Iowa.

After a follow-up chemical test, both animals were declared clear of the brain-wasting disease. Since December's discovery of a mad cow in Washington, a number of countries have suspended imports of American beef, and the U.S. is still negotiating with Japan and others for an end to the boycott.

Some 268,000 screenings are planned over the next 12 to 18 months, and government officials expect more inconclusive findings, due to the sensitivity of the initial tests. These have been designed to cast a wide net to expose potential problems.