HELSINKI (AP) — Authorities in Norway say they haven't been able to detect the cause behind an unexplained disease that is estimated to have killed dozens of dogs in the country in recent days.

The Norwegian Food Safety Authority said Saturday that it had been informed of another six cases of dogs falling ill, with two them already dead, all with the same symptoms of vomiting and bloody diarrhea.

Agency spokesman Ole-Herman Tronerud told public broadcaster NRK that the disease seemed "very serious for a dog. But we don't know yet whether this is contagious or just a series of individual cases."

The Norwegian Veterinary Institute said Friday that it had detected two bacteria in autopsies, but was unable to clarify whether that was the cause of the outbreak.