A team of ACB officials reached Rao's house in Hyderabad on Tuesday morning and took him to their office, where he was interrogated.
ACB Director-General B Prasada Rao told PTI earlier, "He (Pattabhirama Rao) is being questioned by ACB officials."
The ACB has already arrested retired Judge P V Chalapathi Rao and Pattabhirama Rao's son T Ravi Chandra in the cash-for-bail-scandal.
Amid allegations of illegal gratification and corruption against Pattabhirama Rao, the Andhra Pradesh high court suspended him on May 31 while transferring the case to ACB which registered a case against Pattabhirama and seven others including Chalapathi Rao and Janardhan Reddy's elder brother and Bellary city MLA Gali Somashekhar Reddy.
On a tip off that a deal was allegedly struck between Janardhan Reddy, the judge and others, the CBI had recovered cash of nearly Rs 1.60 crore from five lockers here, the keys of which were allegedly in possession of Pattabhirama's son Ravi Chandra.
CBI had also seized Rs 1.14 crore from the possession of T Balaji Rao, brother of Chalapathi Rao.
The CBI had earlier told ACB that Gali Janardhan Reddy's elder brother and Bellary city MLA Gali Somashekhar Reddy, G Dasaratha Ram Reddy, Suresh Babu, an advocate T Aditya and Chalapathi Rao and Pattabhirama Rao and others had allegedly entered into a conspiracy for showing official favour and granting bail to Janardhan Reddy and committed criminal conduct.
The CBI had handed over documents pertaining to the matter to ACB including mobile and land phone numbers allegedly used during finalisation of the alleged deal and duration of conversations.