Poring through bills of lading and records of livestock brands, and tapping into a new national cattle database, Canadian investigators are trying to profile the life of a single cow that has tested positive for mad cow disease, a discovery that has left the North American food industry stunned.
What is known is that the cow was about eight years old and was sick when it was slaughtered. It most recently lived in the northern Peace River region of the western province of Alberta. What is not known is where the cow was born, or how it contracted the illness.
Until those questions and others are answered, the extent of the problem facing the beef industry, from the small Canadian farmer to McDonald's, will remain a puzzle.
The hope is that the case is an isolated incident limited to just one cow, but the mystery, in a country that prides itself on its strict standards, is how the disease got to that cow.
Dozens of federal and provincial investigators based in Calgary and Edmonton are working to crack the case. In the meantime, trade in Canadian cattle has come to a standstill.
"It's like any detective work -- you go from one piece of evidence back to the other and then interview people, ask them what they know, look at their records," said Claude Lavigne, the Canadian Food Inspection Agency's main spokesman for the investigation.
Lavigne would not identify the most recent owner of the cow, but CBC Television said the farm is near the small town of Wanham, Alberta.
So far, investigators have discovered the cow spent time on two other farms, where herds have now been quarantined. Lavigne said he didn't know where the herds are or their sizes.
Investigators have also identified 211 calves that came from the Wanham farm this year.
Those calves will also be separated from their herdmates and quarantined, Lavigne said.
The calves were found using a new nationwide ear tag numbering database designed to quickly trace cattle from birth to death.
But the 2-year-old database does not go back far enough to determine where the infected cow came from.
"This cow was born and sold long before our program was initiated," said Brad Wildeman, chairman of the Canadian Cattle Identification Agency, which runs the ear-tag database.
So investigators have turned to one of the oldest methods for identifying cattle -- their brands.
Scarred into the hips, shoulders or ribs of cattle with a hot iron wielded by their owners, brands have been used by generations of ranchers to identify cattle that traditionally spend summers roaming the range.