A five-day mad cow disease scare that briefly rattled the cattle markets and raised concerns among some beef eaters has been put to rest after sophisticated chemical tests on a suspected animal showed no sign of the brain-wasting ailment.

But the "false positive" in the initial screening again raised questions about the Agriculture Department's testing procedures.

Some critics argued that the department had unnecessarily alarmed the public and beef markets by disclosing the inconclusive preliminary results last week. Others said the testing and government monitoring is inadequate to protect consumers and needs to be strengthened.

The department should find a way "to limit the chances of these faulty test results that put ... producers on pins and needles and our futures markets into full panic mode," complained Sen. Conrad Burns (search), R-Mont.

There has been only one confirmed case of mad cow disease in the United States, a dairy cow found contaminated in Washington state last December. The disease — formally known as bovine spongiform encephalopathy — attacks an animal's nervous system and food contaminated with BSE can afflict people with usually fatal variant Creutzfeldt-Jakob disease (search).

After two suspected mad cow cases last June that also were found to be negative, the Agriculture Department changed its procedures to try to reduce the number of false positive events. It required a second "inconclusive" screening — as it did with the cow last week — before making a public announcement and triggering the more sophisticated chemical tests.

This time around, the cattle markets reacted with some concern but not panic.

"We saw the market sell off and then stabilize," said Bill O'Grady, director of futures research for A.G. Edwards & Sons Inc. in St. Louis. "The market had sort of expected that the odds were high this would end up being a false positive."

Beef futures prices, at 87.3 cents a pound on the Chicago Mercantile Exchange last Wednesday, fell by 2.7 cents after it was announced on Thursday that a potential mad cow case had been discovered. Prices dropped to as low as 84.2 cents a pound before recovering Tuesday to 87.25 cents a pound even before the final tests were made public.

"We're already back to where we were," said Gregg Doud, chief economist of the National Cattlemen's Beef Association.

Virtually no information was disclosed about the cow that was the subject of all the hubbub except that two separate chemical tests at the National Veterinary Services Laboratory (search) in Ames, Iowa, found no sign of mad cow.

That "makes us confident that the animal in question is indeed negative," said John Clifford, deputy administrator of the USDA's Animal and Plant Health Inspection Service.

Since the Washington state case in December, the USDA has screened more than 221,000 animals and no new cases have been found. Like the latest case, the two "inconclusive" findings in June were found to be false positives.

Both the beef industry and the USDA acknowledge that eventually another mad cow case is likely to be discovered among the 40 million adult cattle in the country. About 1 percent of the herd, or 446,000 cattle, are considered in the targeted "high risk" category, according to the USDA, because they are not ambulatory or show signs of some other ailment.

"Chances are that other cases will be discovered" and people are at risk, Carol Tucker Foreman, director of the Food Policy Institute at the Consumer Federation of America, said after Tuesday's announcement.

But beef industry officials said Monday they are confident that consumers are safe from the disease.

"The BSE agent has never been detected in beef," said J. Patrick Boyle, president of the American Meat Institute.

He said the animal parts that can contain the disease — brain, spinal cord and small intestine — are removed and not permitted for consumption. He said he is confident this firewall will protect consumers even if another infected cow is discovered.

Foreman, former assistant secretary of agriculture for food safety, isn't as sure and says "there is no test that can demonstrate meat is free from hazardous tissues."

"Their assurances are based on an assumption that all potentially hazardous tissue is removed from a carcass before it is processed for food," said Foreman.

The rules don't cover all potentially hazardous tissues, don't protect against cross contamination and aren't adequately enforced, he said.