The CBI filed a FIR against Aruna Reddy, a requirement to begin a formal investigation into the matter, said a CBI agency source.
Aruna Lakshmi along with her husband owns the Oblapuram Mining Company (OMC), with a main office in Anantpur town, neighbouring Andhra Pradesh.
Janardhana Reddy was arrested by the CBI on Sep 5 for his role in illegal mining scam in Andhra Pradesh and is currently lodged at the Chanchalaguda jail, Hyderabad.
The FIR against Aruna Lakshmi was registered in Bangalore and came a month the AMC offices were raided by the CBI teams in Bellary and a FIR was registered against Reddy for the first time in Karanataka.
Apart from Aruna Lakshmi, 20 more others are being interrogated, said sources refusing to give out names.
Aruna Lakshmi and others are under the CBI radar after the Supreme Court directive on Sep 23 to the CBI to look into the matter over the linkage between the multi-crore-rupee illegal mining in Anantapur district and Bellary district in Andhra Pradesh.
According to the CBI, the iron ore mined by AMC was routed out through OMC.