The US Department of Agriculture has said a meat sample that resulted in an inconclusive BSE test result last week has tested negative for mad cow disease in further testing.

"We were notified by the USDA National Veterinary Services Laboratories (NVSL) in Ames, Iowa that the inconclusive screening test sample reported on 25 June, tested negative for BSE upon confirmatory testing," said deputy administrator Dr. John Clifford for the Animal and Plant Health Inspection Service.

"This inconclusive result will likely be the first of many to come due to the nature of the surveillance program and the expanded population of cattle being tested for BSE by the USDA," the American Meat Institute said.

"The public, and the markets, need to realise that we're likely to hear more announcements about inconclusive results in the future, and that it is in everybody's interest to not over-react," said J Patrick Boyle, CEO of the AMI.

"Regardless of whether the final test result produces a positive or a negative for BSE, the bottom line is that the animal will never enter the human food supply and that beef remains perfectly safe to eat," he added.