A Dutch vet believed to have died of bird flu was not suffering from a mutated form of the virus, the Dutch health ministry has been quoted as saying.
Millions of birds are being killed
The 57-year-old vet died of pneumonia last week, sparking fears that the bird flu virus might have mutated into a potentially deadly new human form of flu.
But health officials now believe he had contracted only the "normal" form of the bird virus.
The Netherlands has been in the grip of the outbreak for weeks, and the disease has now spread across the border into Belgium.
Belgium authorities announced at the weekend that an extra 270,000 birds were being culled, on top of 250,000 already being slaughtered.
In the Netherlands, some 16 million birds have been killed.
We now know there's no mutation of the virus, we know for sure that the vet died of the original bird flu. It's very good
to know that
Dutch health ministry spokesman
Officials had stressed that there was little danger to human health.
But as well as the death of the vet, dozens of people have now contracted conjunctivitis.
Dutch ministers have announced an independent inquiry into the vet's death.
He became ill two days after working on a farm affected by the bird flu virus.
"We now know there's no mutation of the virus, we know for sure that the vet died of the original bird flu. It's very good to know that," a health ministry spokesman told Reuters new agency.
The vet had not taken anti-viral medicine, as recommended by the government, the spokesman added.
"If he had taken his anti-virals he probably wouldn't have died," he said.
A government statement issued at the weekend said the direct cause of death was chronic pneumonia, but said bird flu virus was also found in his lungs.
Workers are now being offered anti-viral drugs
"No other cause of death could be detected, a clear indication that the man died as a result of infection from this virus," the statement
It added that there were no signs that anyone else has caught the virus from the vet.
Health officials fear that if the bird flu became mixed with human flu viruses the result could be a deadly new form of the disease.
"The contact between the two viruses could produce a new strain," Dutch virologist Albert Osterhaus told Dutch television.
At least 230 Dutch farms have been affected, and despite weeks of precautions, new cases are still turning up, said Dutch Agriculture Ministry spokeswoman Martine de Haan.
The total of 16 million slaughtered birds is now heading towards 20% of the entire Dutch flock of 100 million.
Bird flu is highly contagious among chickens, turkeys and ducks but infects humans only rarely.
A 1997 bird flu outbreak in Hong Kong also spread to the human population, killing six people.
Dutch workers involved in the cull have been vaccinated against the disease, and have been given other medication to help ward off infection.
In Belgium, anti-viral drugs are being offered to vets and others in contact with infected birds.