Two suspects in the murder of a policeman at a check post in the district, were brought here for interrogation on Thursday, amid tight security.
The duo was medically examined at the Thakalai police station and interrogated in connection with the murder of Special Sub Inspector Wilson, police said.
The two men had shot at Wilson using a pistol and stabbed him when he was on duty at the Kaliyakavilai checkpoint on the border with Kerala on January 8.
They were picked up from Udipi Railway station in Karnataka on January 14.
The suspects have been identified as Abdul Shameem (29) and Taufeeq (27), both hailing from Thiruvithancode near Nagercoil.
According to police sources, the duo has confessed to having links with some IS activists from Kerala's Mallapuram and Kozhikode districts.
They were said to be helping them recruit members for the terror outfit.
The police said they were trying to ascertain whether the duo conspired to carry out any attacks in Tamil Nadu.