The operation was a 'routine one' to find out their possible hideouts and prevent infiltration of left-wing extremists from neighbouring states, STF sources aid.
Attapadi in neighbouring Kerala, just 35 km from the dam site, was the scene of a recent Naxal attack.
Tamil Nadu ADGP, T K Rajendran (L and O) had held discussions a few days back and reviewed the preparedness of the force in countering the menace of Naxals and to prevent them from crossing the border.