While the statement issued by the policy-making body of the tax department did not identify the group, official sources named it as the Velammal group.
The CBDT said the group operates "leading educational institutions having a large number of schools and colleges in Chennai and Madurai region".
"The search has resulted in the seizure of around Rs 2 crore of unaccounted cash."
"Out of the unaccounted income detected so far, the group has admitted to having an amount of Rs 532 crore as their undisclosed income," it said.
The searches are temporarily concluded and further investigations are under progress, the Central Board of Direct Taxes (CBDT) said.
The department had carried out search and survey operations against the group at 64 locations in the state early this week.
The charitable trusts of the group are running a medical college and hospital, engineering colleges and schools across Tamil Nadu, the CBDT said.
During the searches, the statement alleged, evidences were unearthed of fee collected under various nomenclatures from students of engineering colleges and schools which were received in cash and not accounted for even as cash receipts were not accounted for in the hospital account.
"Loans and interest were seen repaid in cash which were earlier taken in cash for the purpose of unaccounted investments. These receipts were utilised for the purchase of properties by paying on-money," it charged.
The group, on its official website said, "Velammal is synonymous with quality education from KG to PG." NES KJ