According to sources in the police strike force, personnel have found bunkers and caves where the rebels had been staying. They also found maps of some cities in Tamil Nadu in the valley.
Unconfirmed reports said about Rs nine lakh was found hidden in two farms near the area.
Sources said one rebel group had been staying at Poolangodu, a remote village in the district, by paying Rs 150 as house rent. The Maoists travelled to neighbouring villages in the guise of garment pedlars.
Police said they were studying the strategy used by the Maoists to win over villagers on the basis of information received from the residents of Sempatiyoothu, Periyur and Kallakinaru villages.
Three teams of Special Task Force personnel were also involved in the search in Theni and Dindigul districts.
The three rebels arrested recently in Theni district are being interrogated by the Q Branch in Chennai. A search is also on for seven persons who escaped, police said.