Three persons from Vengaivayal village underwent a voice test at a forensic lab in Chennai on Wednesday.
After obtaining permission from a Special Court on March 25, the CB-CID took the three to Chennai for the test. The agency is investigating the case of the mixing of human faeces with water in a tank that was catering to Adi Dravidar families in Vengaivayal in December 2022.
Previously, 31 persons were subjected to DNA tests, and the voice samples of two persons were taken in connection with the case.