A hand rests on a dog which is lying down on the floor
Up to 40 dogs have been reported with similar symptoms in Norway, and another has reportedly fallen ill in neighbouring Sweden (file picture)

The Norwegian Veterinary Institute said its pathologists found that three dogs showed signs of a bloody gut, and that it had ruled out common causes like salmonella and rat poison.

Food safety authority spokesman Ole-Herman Tronerud told NRK that the illness seemed “very serious for a dog. But we don’t know yet whether this is contagious or just a series of individual cases”.

The agency has advised dog owners to keep animals on a lead in order to avoid contact with other canines.