The panel reportedly asked the NIA finance officials to come along with necessary documents relating to the funds the agency's DG claimed was approved by Jonathan.
The NIA Director-General, Ayodele Oke had claimed that the $50 million found in the apartment belongs to the agency.
The monies - $43.4m, N23m and £27,000 - were recovered by the Economic and Financial Crimes Commission (EFCC) in one of the flats in Osborne Towers, Ikoyi, Lagos.
Oke claimed that the funds were part of the $289,202,382, approved for the NIA in 2015 by former president Goodluck Jonathan.
In heat of the controversy, President Muhammadu Buhari last Wednesday ordered Oke's suspension and set up a three-man panel headed by Osinbajo to get to the root of the matter.
Other members of the panel include the Attorney-General of the Federation, Abubakar Malami and the National Security Adviser (NSA), Babagana Monguno.
According to Punch, the committee had dispatch letters of invitation to Oke's aides, especially those in the NIA finance department, asking them to appear before it on Monday, April 24 (today).
It was learnt that they were also told to come along with necessary documents relating to the funds the DG claimed was approved by the Jonathan administration.
Media reports last Friday had indicated that Oke appeared before the committee that day and told the Osinbajo panel that the $289,202,382 was paid to NIA from the account of the National Petroleum Investment Management Service (NPIMS) on February 25, 2015, on Jonathan's orders.
"We have invited some officials of the NIA to come and explain to us why such a huge amount of money should be kept outside a financial institution," a Presidency source cited by Punch said.
"Some of those invited are from the finance department. The panel hopes to understand the workings of the NIA and how it spends cash relating to projects and security matters.
"The invited persons will also explain what the money was spent on and what sort of security projects the NIA had done which required such a sum of money."
The EFCC Acting Chairman, Ibrahim Magu is said to have submitted his report on the seized monies to the Osinbajo committee.
Details of Magu's report was not disclosed but sources say the EFCC boss has every reason to believe that the $50 million stashed in the Ikoyi apartment was there for suspicious purposes.