Police are on the hunt for the people responsible for the deaths of eight protected wedge-tailed eagles.
The birds were found dead in Conargo near Deniliquin, and a subsequent toxicology report has shown they died from pesticide poisoning.
NSW Environment Protection Authority's Gary Whytcross said all signs suggested the eagles had been deliberately targeted.
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"To find that many birds dead less than forty metres apart is highly suspicious and now with confirmation of pesticide poisoning it certainly looks like this was a targeted attack," Mr Whytcross said.
"Wedge-tailed eagles, like all native Australian birds, are a protected species and it is illegal to harm one. Killing eight eagles with poison is a horrible crime and we want to find whoever did it."
The EPA and police are continuing their investigations.
The poisoning took place in October last year on Willurah Road outside of Conargo, and anybody who saw any "unusual behaviour" are being asked to come forward.
Anybody with any relevant information can call the EPA Environment line on 131 555, Deniliquin police on 03 5881 9299 or CrimeStoppers on 1800 333 000.