Ammal, 84, has been given an option to present her case through an authorised legal representative, in case she cannot come herself and answer questions of agency sleuths on March 28 here, sources said.
The agency, they said, wants to investigate the role of Ammal with regard to alleged channelling of Rs 200 crore to the DMK family-run Kalaignar TV through a circuitous route in which her daughter Kanimozhi and MD of the TV group Sharad Kumar are also accused.
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The DMK supremo's wife has, however, denied any wrongdoing in this case.
A charge sheet in this case, under provisions of Prevention of Money Laundering Act (PMLA), is pending at present.
The agency has already questioned Kanimozhi and former Telecom Minister A Raja in this regard.
Both the DMK leaders and others have been questioned by ED about the alleged transfer of Rs 200 crore to the TV channel, in which Kanimozhi and Sharad Kumar each hold 20 per cent stake.
ED had earlier also scrutinised documents related to both the DMK MPs' incomes, properties and personal investments.
It had also initiated attachment proceedings under PMLA against other individuals and certain telecom firms involved in the case.
Besides the cases of Raja and Kanimozhi, a similar probe is underway under the provisions of the anti-money laundering Act against Asif Balwa, Director of Kusegaon Fruits and Vegetables Pvt Ltd, Rajeev Agarwal and Karim Murani of Cineyug Films (Pvt) Ltd.