More than 50 tigers in a Thai zoo have been put down after they showed symptoms of bird flu.
The zoo has been closed to visitors since the outbreak began
The animals became sick after eating raw chicken carcasses believed to have been infected with the virus.
Before the outbreak began, the Sriracha Tiger Zoo in Chonburi province housed more than 400 endangered tigers, but 80 have now died or been culled.
No keepers have succumbed to the virus, and the WHO said the outbreak among tigers had no implications for humans.
According to wildlife officials, 32 of the tigers in the zoo actually died of the H5N1 bird flu virus earlier this week, and more than 50 were put down after showing signs of the disease.
"We had to perform mercy killings on those tigers because
they were in critical conditions," said Preecha Ratanaporn.
But he indicated that the worst of the outbreak was now over, saying: "We are monitoring four or five more of these tigers. If they show no symptoms in a week, we can declare the zoo free of bird flu."
H5N1 BIRD FLU VIRUS
Principally an avian disease, first seen in humans in Hong Kong, 1997
Almost all human cases thought to be contracted from birds
Isolated cases of human-to-human transmission in Hong Kong and Vietnam, but none confirmed
Sriracha Zoo has been closed to the public since Tuesday, and the remaining tigers are reportedly being fed pork instead of chicken.
The Thai government - like several others in the region - has battled a string of bird flu outbreaks this year.
At least 11 Thai people are known to have died after contracting a human form of the disease.
More than 100 million birds have been culled across south-east Asia in an attempt to control the virus.