As many as 100 chickens were found dead at a poultry farm in Vehloli village of Shahapur tehsil in Thane district on Friday.
The samples have been sent to a lab in Pune considering the bird flu threat.
Officials informed that around 25,000 birds falling in a kilometre radius of the affected poultry farm will be killed within the next few days.
The district animal husbandry department has been ordered to take measures to control the infection.
Thane District Collector Rajesh Narvekar has assured that there was no cause for concern in other parts of the district in Maharashtra.
â€œThe district administration has issued a notification for the culling of birds in the farms within a one-km radius of the affected farm,â€ Narvekar added.
Apart from bird flu cases reported from Shahapur, no cases have been detected in any other part of the district, he said, assuring people there was no cause for panic.
In compliance with the standard operating procedure at least 15,600 broiler birds had been culled in Shahapur till Friday morning.
Apart from this, 7,962 layer birds, 20 ducks, 980 eggs, litter feed, etc have also been culled, he said, adding that the process of culling is underway. The district administration is monitoring the situation closely to prevent the spread to other locations, the official said.