Officials have confirmed dozens of dogs have died in the past few days by the unknown illness. The Norwegian Food Safety Authority added another six cases of dogs falling ill have been reported. At least two of the dogs already dead, all with the same symptoms of vomiting and bloody diarrhoea.
The disease has been called “very serious for a dog”.
Agency spokesman Ole-Herman Tronerud told public broadcaster NRK: “We don’t know yet whether this is contagious or just a series of individual cases”.
Many cases have been reported around the capital Oslo.
The cities of Bergen and Trondheim, and the northern Nordland municipality, have also been affected.
The Norwegian Veterinary Institute said on Friday that it had detected two unspecified bacteria in autopsies.
However, it has not been confirmed whether this was the cause of the outbreak.
The institute’s emergency and safety director, Jorun Jarp, said: “To have healthy and great Norwegian dogs die so quickly is naturally serious.
“It’s a very special situation I haven’t been involved in before.”
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Heartbroken owners have shared their experiences of losing their beloved pets.
Torstein Holten of Hamar was the owner of a seven-year-old pointer named Lexi.
He told Norwegian state broadcaster NRK on Friday that Lexi had been all of energy when she went out running with her last Monday.
But on Tuesday, she developed diarrhoea and started throwing up.
He took her to a vet on Thursday, where she was treated for several hours.
The family was told they could take her home but bring her back if her condition worsened.
The next morning the Holten family found Lexi dead in the hallway.
Mr Holten said: “There’d been no earlier sign of any problems.
“There will be no hunting this year.
“This is very sad, she was a member of the family.
“There were lots of tears at our house Friday morning.”