Dog owners in Norway are being warned after a mysterious illness caused the death of a number canines in locations across the country, officials said Monday.

The Norwegian Food Safety Authority said that they are performing autopsies on some of the dogs who perished to look for possible causes such as viruses, bacteria, fungi, and parasites.

All dogs had clear signs of serious bowel disease, according to The Norwegian Veterinary Institute.

They were taken to their vets after suffering from severe diarrhea and their conditions worsened rapidly.

People in Norway are being asked to restrict close contact between dogs.