Those grilled so far are two former Group Managing Directors (GMDs) and three former Executive Directors (EDs) of the NNPC.
Those interrogated so far are two former Group Managing Directors (GMDs) and three former Executive Directors (EDs) whose names were withheld so as not to jeopardise the investigation.
Former Minister of Petroleum Resources, Mrs. Diezani Alison-Madueke allegedly ordered the transfer of the money.
One of the former executive directors is said to have admitted playing a role in the transfer of the money, the report said, citing an EFCC source.
"We are however not stopping at this bend because we discovered that some of these officials were used for many illicit transactions," the source said.
"By the time we extend our investigation to crude oil lifting, you will appreciate the sleaze during the tenure of Diezani as minister of Petroleum Resources. A syndicate was used to perpetrate the fraud in the oil firm."
According to the report, the interrogation of the former officials was confirmed by a source at the NNPC.
The source said: "This corporation is following the development. The EFCC is on top of the $153million palaver; it has actually been inviting some of our past officials for questioning.
"The good thing is that some of these former officials are still on NNPC’s pension roll. They can be recalled at any time for clarification of some issues."
The source, however, refused to give names of those quizzed by the anti-graft agency, saying he would have to obtain authorization from the administration and security departments.
On the ruling of a Federal High Court on the $153million, the source said the NNPC cannot react to it without "getting necessary legal advice."
"Our board is meeting on the $153million saga and other matters on January 30. What we are doing now is to get the proceedings of the Federal High Court of Friday. We have a very articulate Legal Department which will study it.
"NNPC is a corporation with a board and a chairman. The legal advice will determine our next step after the board’s meeting.
"If the court indicts any former officials, the corporation can still exercise disciplinary control on them," the source added.
Meanwhile, the EFCC has reportedly started the process of seizing large estate in Yenagoa, Bayelsa State traced to Diezani.
It was gathered that the asset will be placed on temporary forfeiture pending the arraignment and trial of the ex-minister either in Nigeria or in the United Kingdom.
An EFCC source was quoted as saying: "Since we recorded the breakthrough, our legal unit has been working round the clock on how to seek the nod of the court for a temporary forfeiture order.
"We have obtained relevant data from Bayelsa State Geographic Information System. As a matter of fact, the estate is coded as BGIS/OK/02/16/310 by the agency.
"We will file the required application for the seizure of the estate pending the arraignment and the conclusion of the trial of the ex-Minister. This is a standard benchmark allowed by the law. We are certainly heading for the court."
On Friday, January 6, a Federal High Court in Lagos ordered the temporary forfeiture of the sum of $153,310,000, that Diezani allegedly siphoned from the NNPC.
The money was said to have been stashed in three Nigerian bank accounts.