Dr. Ron DeHaven, chief veterinarian for the Agriculture Department, said Canadian officials have provided records that indicate the animal was one of a herd of 74 cattle shipped from Alberta, Canada, into this country in August 2001 at Eastport, Idaho.
"These animals were all dairy cattle and entered the U.S. only about two or two-and-a-half years ago, so most of them are still likely alive," DeHaven said.
DeHaven emphasized that the sick cow's presence in that herd does not mean all 74 animals are infected. Investigators are tracking down where the other 73 animals are.
"We feel confident that we are going to be able to determine the whereabouts of most, if not all, of these animals within several days," DeHaven said.
Canadian officials said at a news conference Saturday it's still too soon to conclude the cow was infected in their country.
"It would be premature to draw such conclusions at this time," Dr. Brian Evans, chief veterinary officer of the Canadian Food Inspection Agency, told reporters in Ottawa.
"What we're dealing with at this point in time is not full-bodied information," he said. "We want to be thorough, we want to be accurate ... that's what the U.S. expects of us and that's what we expect of them."
Food safety advocates criticized the U.S. system for tracing the origin of animals slaughtered for food, reports CBS News Correspondent Wyatt Andrews.
"The gaps in this system for protecting the public are huge," said Caroline Smith DeWaal, food safety director for the Center for Science in the Public Interest.
She and other experts believe the government has taken too long adopting so-called animal trace-back technology, which the U.S. says it is working on, and which could quickly locate and identify all other cows that may be a mad cow threat.
"If we can't identify the cattle that potentially were infected at the same time this one was the USDA really cannot protect the public," Smith DeWaal said.
The former inspector general of the Agriculture Department, Roger Viadero, says the government could know where every suspect cow came from and where every bit was sold, but never pursued the system.
"In ten minutes they should have been able to tell where the animal came from and where it went," said Viadero.
Confirming that the sick cow came from Canada will be crucial for the United States to continue exporting beef because it could retain its disease-free status. The country has lost 90 percent of its exports because of the case, the National Cattlemen's Beef Association estimates, because more than two dozen foreign nations have banned the import of U.S. beef despite claims by U.S. officials that the meat is safe.
Canada found a case of mad cow disease in Alberta in May. The discovery decimated the country's beef industry as its importers cut off trade.
Dr. Brian Evans, chief veterinary officer of the Canadian Food Inspection Agency, said it's premature to draw any conclusions about the cow's origins because Canadian and U.S. records that ostensibly refer to the same cow don't agree on key details.
Based on the Canadian records, the diseased cow was 6 1/2-years-old - older than U.S. officials had thought, DeHaven said. U.S. papers on the cow said she was 4- or 4 1/2-years-old.
The age is significant because the United States and Canada have banned feed that could be the source of infection since 1997.
Farmers used to feed their animals meal containing tissue from other cattle and livestock to fatten them. Countries have banned such feed because infected tissue - such as the brain and spinal cord - could be in the meal.
Mad cow disease, formally known as bovine spongiform encephalopathy, is a public health concern because it is related to a human disease, variant Creutzfeldt-Jakob. In Britain, 143 people died of the human illness after an outbreak of mad cow in the 1980s. People can get it if they eat meat containing tissue from the brain and spine of an infected cow.
The Agriculture Department insists the meat supply is safe because parts that carry the disease - the brain, spinal cord, and lower part of the intestine - were removed before the meat was processed.
But as a precaution, the government has recalled an estimated 10,000 pounds of meat cut from the infected cow and from 19 other cows all slaughtered Dec. 9 at Vern's Moses Lake Meat Co., in Moses Lake, Washington.
CBS News Correspondent Joie Chen reports the meat was shipped to four Western states.
Ken Peterson, of the agriculture department's Food Safety and Inspection Service, "it's too early to know how much of the product has been brought back, though we know that some of the product is beginning to be at least held at the retail facilities."
Officials say the slaughtered cow was deboned at Midway Meats in Centralia, Oregon, and the meat was sent to two other plants in the region, identified as Willamette and Interstate Meat, both near Portland, Oregon.
The animal most likely became sick from eating contaminated feed, so the Food and Drug Administration is tracking down what it ate. That's a difficult task because the cow may have gotten the disease years ago, long before it showed signs that it was sick. The disease has an incubation period of four or five years.
Dr. Stephen Sundlof, head of the FDA's Center for Veterinary Medicine, said the agency also is trying to account for all of the products made from the cow. This includes items like soap and soil.
Gregg Doud, an economist for the National Cattlemen's Beef Association, said Friday that the United States stands to lose at least $6 billion a year in exports and falling domestic prices.
Egypt and Kuwait are among two dozen buyers blocking American beef.
A U.S. delegation was to leave Saturday for Japan, which takes about one-third of all U.S. beef exports, and possibly other Asian countries that imposed bans on American beef and livestock this week. The Treasury Department said it is monitoring developments.
Federal officials on Friday quarantined a herd of 400 bull calves, one of which is an offspring of the sick cow.
One calf is still at the dairy near Mabton, Washington, that was the final home of the diseased Holstein cow. That herd was quarantined earlier. Another calf is at a bull calf feeding operation in Sunnyside, Washington, and a third died shortly after being born in 2001, DeHaven.
It is considered possible but unlikely that the infected cow passed the disease onto its calves.