Washington ? Authorities said Monday they were looking for links between the Holstein infected with mad cow disease and a Canadian cow that was diagnosed with the deadly illness in May.

Repeating their insistence that the U.S. food supply is safe, agriculture officials also said they are searching for 81 Canadian-born cows from the same herd as the sick Holstein that records indicate entered the United States in late 2001.

Dr. Ron DeHaven, the Agriculture Department’s chief veterinarian, said records from the Washington dairy farm that was the infected cow’s last home, and in Canada, confirm that the animal was born in April 1997 in Alberta, Canada. Alberta also was the home of the infected Canadian cow.

More significantly, both cows were born before the United States and Canada began banning from use in cattle feed brain and spinal cord tissue that is the primary means by which the ailment is transmitted. The ban, which took effect in August 1997, prohibits feeding the cattle protein to cattle, sheep and goats.

“No doubt that will be a very important component of the investigation,” DeHaven said, adding that it was premature to conclude there were any ties between the two diseased cows.

DeHaven said that DNA studies now under way would provide more evidence on the origin of the cow that was infected. They also are examining records of the herd that included the infected cow.

For their part, Canadian officials were awaiting results of DNA tests before acknowledging the cow’s Canadian provenance. But Dr. Francine Lord, an animal health expert with the Canadian Food Inspection Agency, said any link between the cases would mark an important advance in trying to find the source of the disease.

Canadian investigators have been unable to pinpoint the source of the infection. The infected Canadian cow was between 6 and 8 years old.

Lord said the tainted feed that was believed to be source of the infection could have come from either country, noting a brisk cross-border trade in animals and related products. “That’s why we consider this a North American issue,” Lord said.

Dave Solverson checks on his herd of cattle on his feed lot west of Camrose, Alberta, Canada. Investigators have tentatively traced the first U.S. cow with mad cow disease to Alberta, a factor that could help determine the scope of the outbreak and might even limit the economic damage to the American beef industry.

The Food and Drug Administration also has said that only 75 percent of animal feed producers were complying with the cattle-parts feed ban when it went into effect, but that compliance has improved to close to 100 percent.

The Canadian cow showed signs of the disease at slaughter and Canadian officials prevented its meat from being sold for human consumption.

Not so with the case of the Washington state cow. Dr. Kenneth Petersen, a USDA veterinarian, said Sunday the government’s investigation revealed that meat from the infected dairy cow could have reached retail markets in Alaska, Hawaii, Idaho and Montana and the territory of Guam, in addition to Washington, Oregon, California and Nevada.