WASHINGTON (CNN) -- The Holstein diagnosed with mad cow disease [red]may have[/red] entered the United States from the Canadian province of Alberta in 2001 with 73 other cows, an official with the U.S. Department of Agriculture said Saturday.

Ron DeHaven, the USDA's chief of veterinary medicine, said Canadian records show the herd would have entered the United States at Eastport, Idaho. The cow was part of a herd in Washington state before being sent to slaughter.

He said investigators have matched an ear tag retrieved from the sick cow at the slaughterhouse to records from a Canadian cow.

Dr. Brian Evans, chief veterinary officer with the Canadian Food Inspection Agency, said Canadian and U.S. investigators differ on the cow's age.

The owner of the herd in Washington told federal authorities that the cow was 4 to 4-1/2 years old, but Canadian records show that the suspect cow from the Canadian herd was born in 1997, making it at least 6 years old, DeHaven said.

The cow that became ill had had three calves, one of which died at birth, DeHaven said.

Canadians say their cow had only two calves.

Tests to analyze the cow's DNA and determine its herd will not be known for about a week, Evans said.

"We do not have a definitive diagnosis of this particular animal," Evans added in a conference call with reporters.

In Canada's first mad cow case in a decade, an 8-year-old cow that was slaughtered in [red]January[/red] after showing signs of illness tested positive for BSE in May. Tests in England confirmed signs of mad cow disease. Eighteen farms were quarantined, but no additional cases were discovered.

After the diagnosis, the United States banned imports of beef from Canada. The ban was partially lifted in September.

DeHaven said investigators are uncertain whether they have located the birth herd, which would allow them to test other animals. The tests for mad cow disease, also known as bovine spongiform encephalopathy (BSE), cannot be done on a living animal.

[red]"These animals were all dairy cattle and entered the U.S. only about two or two-and-a-half years ago[/red], so most of them are still likely alive," DeHaven said.