All seven patients admitted to hospital for checks after an outbreak of a lethal form of bird flu in Malaysia have tested negative for the disease, Health Minister Chua Soi Lek said today.

Three had already been discharged and a government veterinary surgeon and her three children were expected to leave hospital Monday, Chua told reporters.

"They are free from avian flu. They don't have fever any more. There are no more suspected cases," he said.

"I must emphasise that until now only chickens have been found with avian flu. No humans are infected."

The government announced on Thursday that the H5N1 strain of avian influenza had been discovered for the first time in Malaysia, in chickens in the village of Baru Pasir Pekan near the border with Thailand where eight people have died of bird flu this year.

The disease has also killed 19 people in Vietnam, and the World Health Organisation fears the virus could mutate into a highly contagious form that triggers the next global human flu pandemic.

Malaysia says the bird flu was restricted to the one village, with the two affected birds having recently been taken into Thailand for a cock fight.

Hundreds of birds in the village and surrounding area have been culled and veterinary officials have launched a national inspection of poultry farms, commercial enterprises and bird parks.

'No need for panic'

The World Health Organisation (WHO) said it was "troubled" by the outbreak in Malaysia, which had implemented aggressive measures to prevent importation of the virus.

"H5N1 has once more shown how well it is entrenched in parts of Southeast Asia," said the WHO's regional director for the Western Pacific, Shigeru Omi.

"It is going to be a long and difficult struggle to eliminate this virus from the environment. And the longer it takes, the greater the risk to public health.

"As long as the virus circulates in poultry this way, there will be a risk of it jumping to humans, with the potential for a pandemic influenza strain," he said.

Omi, who was attending a conference in Penang in Malaysia today, said the reported discovery of bird flu in pigs in China had taken the world closer to a global human flu pandemic but there was no need to panic at this stage.

"Of course it's a little bit closer but how close we don't know. This is one factor we have to monitor very closely."