CBI court judge B M Angadi extended the judicial custody of Reddy and his personal assistant after the CBI filed an application seeking extension of their custody.
Associated Mining Corporation and Deccan Mining Syndicate owned by Reddy and his wife Aruna Lakshmi have been facing probe over charges of illegal mining.
Former minister and Congress leader V Muniyappa and some others are the other accused in the case.
Reddy is currently lodged in Bangalore Central Prison at Parappana Agrahara on the city outskirts.
