Knut-André Haugen found two dead swans with their heads under their wings outside Fredrikstad. Now the Norwegian Food Safety Authority suspects further spread of bird flu.

Bird flu, or avian influenza, has struck the Swedish poultry industry hard this winter. Since November, thousands of turkeys and more than one million chickens have been culled. Malin Grant, an epidemiologist at the National Veterinary Institute, says the virus can be deadly for domestic poultry but the strains currently circulating don't easily infect or spread between people.

The particularly dangerous strain of avian influenza virus H5N8 has been detected in a mute swan found on the Kopli peninsula in Tallinn.

Dozens of dead eiders have been found along the coast in Eastern Norway. The preliminary autopsy report shows no signs of bird flu, but the birds are thin and emaciated.