The CBI, given the MP's custody for five days, took him from Chanchalguda Central Jail to its office at Koti, three kilometre away. The questioning took place in the presence of Jagan's lawyers.
After questioning him for over six hours, Jagan was dropped back at the jail amid tight security. He was questioned Sunday at the office of the director general of prisons near the jail.
The agency wants to know from Jagan about the investments that flowed into his companies between 2004-09 when his father Y.S. Rajasekhara Reddy was the Andhra Pradesh chief minister.
The businessman politician allegedly got the investments as bribe for the favours doled out by the government to investors in the form of land, licences and other concessions.
The CBI believes a part of the bribe money was sent abroad to what are known as "paper/briefcase companies" and routed back into Jagan's firms through hawala.
The funds were pumped in by some companies based in Luxembourg and Mauritius.
Jagan allegedly received investment of Rs.1,234 crore in his cement, power and media companies.
The CBI sleuths are believed to have questioned him about the investments made by Vanpic promoter Nimmagadda Prasad on quid pro quo basis. Vanpic was allotted thousands of acres of land in Guntur and Prakasam districts for two port projects.
Mopidevi Venkataramna, who as then minister for infrastructure and investment, had signed orders granting concessions to Vanpic, Prasad and bureaucrat K.V. Brahmananda Reddy are already in judicial custody.
Jagan was arrested by the CBI May 27. The next day a CBI court sent him to judicial custody till June 11. The probe agency later got his custody for questioning.
The CBI court adjourned the hearing on the bail petition of Venkataramna till Tuesday. The CBI, countering the bail petition, said if released on bail, the accused may tamper with the evidence.
The investigating agency told the court that Venkataramna acted with a criminal conspiracy and caused losses to the public exchequer. He played a key role in clearing Vanpic project in violation of the rules.
Venkataramna was excise minister when he was arrested by the CBI May 24. He resigned the same day.