With the disease now at Europe's doorstep, experts from the World Health Organisation (WHO) have arrived in Turkey but bad weather forced them to delay a trip to the infected areas.
Recep Akdag, the health minister, said on Saturday that the virus had been detected in a fourth person, currently under treatment in a hospital in the city of Van, after officials confirmed three human cases on Friday.
He did not specify whether the virus was the lethal H5N1 strain blamed for the death of two siblings in the same hospital over the past week, the first human fatalities of bird flu outside Southeast Asia and China.
"There are four cases confirmed by the labs ... two are dead, as you know, and the other two are still living," Akdag told the public TRT television.
Results from a third sibling who also died were negative.
The three children, aged between 11 and 15, died after playing with the head of a slaughtered chicken, which the family ate after it fell sick.
"There are four cases confirmed by the labs ... two are dead, as you know, and the other two are still living"
Turkish health minister
They lived in the town of Dogubeyazit, 45km (28 miles) from the border with Iran.
From the patients undergoing treatment in Van, 26 were from Dogubeyazit, four from nearby Igdir and three others were from Van, Akdag said.
No human transmission
As panic spread across the country and the culling of fowl continued, Akdag sought to allay fears that the virus might have been transmitted between humans.
"The data we have at the moment gives no indication that the virus is being transmitted between humans," he told reporters in Ankara. "We do not expect an epidemic that will affect the whole public."
Currently, humans are thought only to contract bird flu if they come into close contact with infected birds, but scientists fear that millions around the world could die if the virus crosses with human flu strains to become highly contagious.
Akdag was scheduled to accompany a WHO delegation to Van, but their flight was postponed to Sunday due to heavy fog.
The experts would see "if we are faced with the first case of human-to-human transmission," a WHO spokeswoman said on Friday, even though the initial hypothesis was that the children were infected from sick chickens.
Despite several suspicious cases in other parts of the country, "there are no probable or highly probable (human) cases in Turkey other than the patients in Van," Akdag said.
Mehdi Eker, the agriculture minister, meanwhile, announced that bird flu had been detected in two more regions in the east, where 14,000 birds had already been slaughtered.
Role of poverty
Samples from wild pigeons in the provinces of Erzincan and Bitlis tested positive for the disease, Eker said, without specifying whether it was the H5N1 strain.
British lab tests have confirmed
H5N1 is in the Turkish poultry
Flu cases among birds have been detected in three other areas in eastern Turkey, as well as a town in the southeast and in a region close to the capital Ankara, in the west.
The European Commission said tests at a British laboratory confirmed the presence of the H5N1 strain in poultry in the eastern region where the two dead children lived.
Eker said "the social-economic characteristics of the region and the low level of education" of its people were complicating the battle.
The east and southeast are Turkey's most impoverished regions, where people breed poultry in their households for their own consumption.
Press reports have suggested that official warnings might fail to produce the desired impact as many in the predominantly Kurdish area do not speak Turkish.
The sub-type H5N1 is the strain responsible for the deaths of more than 70 people in Southeast Asia and China since 2003, nearly 40 of who succumbed last year alone.
The first of the Turkish victims, Muhammet Kocyigit, 14, died on Sunday, followed five days later by his 15-year-old sister Fatma.Their sister Hulya, 11, succumbed on Friday after several days in intensive care.