The three pets were let out Tuesday evening to relieve themselves in the backyard of a southwest-area home, but one of them became violently ill when it came back inside.
A second dog also became sick, but the third canine is recovering.
A veterinarian determined the animals had eaten poisoned sausage.
City Animal Services staff and the Calgary Humane Society are helping with the police investigation.
People in the area are being urged to keep a close watch on their pets. (CHQR)