If the tests prove positive, it will spark fears that the virus has now spread across Turkey to a city estimated to have some 15 million residents. Mehmet Bakar, Istanbul province deputy health director has said that initial tests on two dead chickens in the Istanbul district of Kucukcekmece indicated they were infected by the bird flu virus.
A third test was being carried out to determine the definitive diagnosis.
"Twenty-one people under suspicion (of having bird flu) have been kept in hospital under observation. Samples have been taken from these people and sent to the laboratory for examination," Bakar was quoted as saying in Star newspaper.