The panel probing the recovered Ikoyi 'loot' were grilled by Osinbajo, Attorney-General Abubakar Malami, and the NSA, Babagana Monguno.
President Muhammadu Buhari had on Wednesday set up a three-man panel headed by Osinbajo to unravel the truth behind the $50 million retrieved from one of the flats in Osborne Towers, Ikoyi Lagos.
The committee on Thursday questioned the Director-General of the Department for State Services (DSS), Lawal Daura; Inspector-General of Police (IGP), Ibrahim Idris; and the Acting Chairman of the Economic and Financial Crimes Commission (EFCC), Ibrahim Magu.
The two other members of the panel, the Attorney-General of the Federation (AGF), Abubakar Malami, and the National Security Adviser (NSA), Babagana Monguno, were also said to be part of the questioning.
Details of the meeting were not available at the time of filing this report.
Last week Wednesday, operatives of the EFCC discovered $43.4 million, N23 million and £27,000 in the Ikoyi apartment in a raid aided by a whistle-blower.
Many high-profile Nigerians, including the Minister of Transportation, Rotimi Amaechi and a former chairman of the Peoples Democratic Party, Adamu Mu'azu, were fingered as owners of the cash, but all denied its ownership.
Consequently, the orphaned monies found a claimant - the National Intelligence Agency (NIA).
The Director-General of the agency, Ayodele Oke had claimed that the funds were approved for the agency by former president Goodluck Jonathan for 'cover operations'.
But Oke, who has been suspended by the President, failed to answer many questions - some of which were; why was the money kept in a random apartment believed to have been acquired by his wife, Folashade? Why was the current President not informed about the cash? Why was the money unused for two years?
Buhari has given the Osinbajo panel two weeks ultimatum to find answers to these questions and more.