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.
[...] 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.
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.