Mr Obiano, whose tenure ended last week Thursday, was intercepted and arrested at the Murtala Mohammed International Airport in Lagos after handing over power to Governor Charles Soludo same day while on his way to the United States.
On Monday, the chairman of the anti-graft agency, AbdulRasheed Bawa, said he was still being detained for not meeting the bail conditions granted to him, dispelling rumors of political persecution.
An operative who leaked a video clip of the former governor on red short and white T-shirt drinking water while being detained at the facility of the EFCC is said to be undergoing disciplinary measures.
On Wednesday night, Mr Obiano was released and his passport confiscated as part of his bail conditions.
He is reportedly being probed over alleged misappropriation of public funds, including, N5 billion Sure-P and N37 billion security vote which was withdrawn in cash.
Declining comments, Mr Bawa said the EFCC will not reveal why Mr Obiano is being investigated because the anti-graft agency is being accused of media trials in the past, a habit he said will not continue under his watch.
“I don’t know what update you want me to give, because you have been accusing us of media trials, and you want me to say we are doing this and that. No, we (EFCC) would not do that. We would continue to do our investigation professionally as we have been doing,” Mr Bawa told journalists in Abuja.
Part of the funds, the News Agency of Nigeria (NAN) reported, was also allegedly diverted to finance political activities in the state.
His successor recalled inheriting about N300 million and over N109 billion debt from the former governor.