Four people are being tested for suspected bird flu in Malaysia after developing fevers near the site of two outbreaks in poultry, officials said today.

The four are in quarantine in two hospitals in the northern state of Perak, they said.

"They will be quarantined for a few days. We need to ascertain the cause of their fever," said Health Ministry disease control department director Ramlee Rahmat.

"The (test) results will be known by Sunday," he added.

More than 90 people have died from bird flu in China, Southeast Asia, Iraq and eastern Turkey since 2003. So far, there have been no human deaths in Malaysia due to the virus.

Ramlee said one of the suspected victims was a 43-year-old chicken breeder who lives a kilometre (about half-a-mile) from an outbreak in Changkat Tualang village, and another was his seven-year-old neighbour.

The other two live about 10 kilometres from the Laketown Resort nature reserve where the disease has also been discovered.

Veterinary officials have slaughtered tens of thousands of birds at both sites since the outbreaks were discovered on Thursday.

Birds on trees and flying away

However, state veterinary officer Wan Mohamad Kamil said his colleagues were finding it difficult to kill all the birds in the affected areas, with some staying in trees and others flying away.

"We have a problem. Some of the birds are high up on the trees and others are migrating to neighbouring villages," he said, adding that 41,979 poultry have been killed so far.

"Police and wildlife departnment officials have been roped in to destroy the birds," Wan Mohamad said.

Perak has one of the the biggest duck and chicken industries in the country and exports poultry to neighbouring Singapore.

H5N1 was detected last month in 40 free-range chickens in four villages on the outskirts of Kuala Lumpur, the first outbreak in more than a year.