A team of I-T officials from Perambalur, about 150 km from here, were conducting searches at the house of Ratnam from around 6 am, official sources said.
The searches are going on, they said declining to give any further detail.
CBI had on December 22 arrested Ratnam and another quarry contractor Ramachandran, and Reddy's auditor Premkumar following investigations in connection with recent Income Tax searches at his residence and office in Chennai that resulted in seizure of 127 kg of gold and over Rs 170 crore in cash post-demonetisation.
The five have been accused of converting the unaccounted cash held by them in old currency notes to new notes with the help of unknown public servants from different banks within 24 days from the date demonetisation was announced (November 8).