The Taitung Animal Disease Control Center chief Li Huan-tang said Monday that tests of grain particles retrieved from the stomach of the dead birds last week found them to contain trace amounts of the pesticide carbofuran.

The center therefore determined the dead birds were killed by the chemical, one of the most toxic carbamate pesticides marketed in Taiwan that is used to kill insects during the period when rice and vegetable seedlings are being cultivated.

Taitung County Agriculture Department head Hsu Rui-kuei said after the findings were made public that the National Police Agency has launched an investigation to determine if the birds were illegally poisoned to death.

Wu Chia-wen, a division chief of the agency’s Seventh Special Police Corps., told CNA that the farmer, a tenant from outside the county, said he never used chemicals in the field because of his dedication to organic farming.

Nearby farmers also said they did not use pesticides, Wu said, and no carbofuran residue has been found so far in the area, giving police little to go on in their search for the source of the poison.

The investigation is being expanded in the hope of unearthing the truth, the police officer said.

Most of the dead birds were spotted munia, according to the Wild Bird Society of Taitung, which was invited by the local government to help identify the birds.

Other species found among the dead birds were sparrows, red turtle doves, spotted doves, white-rumped munia, and white-breasted waterhens, as well as two ring-necked pheasants which are a protected bird species in Taiwan.