A follow-up government test found no sign of mad cow disease (search) in an animal singled out in preliminary screening last week, the Agriculture Department said Wednesday.

Officials declined to provide any additional information about the animal. Tests on a second carcass, also singled out in preliminary testing as possibly being infected, was pending and will not be available for several days.

"The USDA (search) remains confident in the safety of America's food supply," said John Clifford, deputy administrator of the department's Animal and Plant Health Inspection Service (search).

Clifford said tests by the federal laboratory at Ames, Iowa, on tissue from the carcass screened last Friday were negative.

"No further details such as what type of animal, where the animal came from or what lab did the (initial) testing would not be disclosed," said Clifford.