Rammohan Rao’s residence in Anna Nagar, Chennai. Credit: ANI/TwitterThe income tax department raided the Chennai residence of Tamil Nadu chief secretary Rammohan Rao on Wednesday morning.IT raid at Tamil Nadu Chief Secretary Rammohan Rao's residence in Anna Nagar(Chennai) pic.twitter.com/A0otFuXI8Y— ANI (@ANI) December 21, 2016According to the Indian Express, it has been alleged that Rao had close links with AIADMK functionary and businessman Shekhar Reddy, whose businesses and residence were raided by the IT department earlier this month. The raid on Reddy proved to be the biggest post-demonetisation seizure, with Rs 34 crore currency in Rs 2,000 notes and 167 kg of gold recovered. The CBI and Enforcement Directorate, who carried out the raid jointly, had underestimated what they would find.Sources told NDTV that it was the findings from the raid on Reddy that raised questions about Rao.Fifty-eight-year-old Rao, who earlier served as the additional chief secretary to the chief minister, was made chief secretary in June this year.According to NDTV, seven other locations associated with Rao were also raided early on Wednesday morning, including the homes of his relatives.CNN-News18 quoted DMK secretary M.K. Stalin as saying in a statement that this caused “disgrace” to Tamil Nadu. “This is perhaps for the first time a raid is conducted at a CS place in TN,” he said.West Bengal chief minister and Trinamool Congress leader Mamata Banerjee condemned the move on Twitter, calling it an attack on federalism. She also questioned why no members the BJP had been raided.Why this vindictive, unethical, technically improper action? Is it only to disturb the federal structure? 2/6— Mamata Banerjee (@MamataOfficial) December 21, 2016While corruption needs to be condemned strongly, raid on TN Chief Sec by Central agencies devalues institution of head of civil service 4/6— Mamata Banerjee (@MamataOfficial) December 21, 2016… and removing him from the post prior to any preemptive action, based on information 6/6— Mamata Banerjee (@MamataOfficial) December 21, 2016