The acting chairman of the Economic and Financial Crimes Commission (EFCC) said a "generation of looters" was supporting a former petroleum minister, Diezani Alison-Madueke, whom the EFCC seeks to extradite to Nigeria to face trial for corruption.
Mr Magu spoke with journalists on Monday in Kaduna, according to a report by PUNCH newspaper.
Mr Magu in January had alleged that some foreign countries were sabotaging the efforts of the commission in prosecuting Mrs Alison-Madueke by giving her protection.
However, he said the EFCC is working with foreign security outfits to bring the former minister back to Nigeria.
Mr Magu said he had informed the UK government during a visit to the country that Nigeria needs the ex-minister's alleged loot to boost its economy.
"It was unfortunate she stole not less than $2.5 billion and has a generation of looters supporting her.
"I was in London this year, we did an investigation together with the UK team, and anywhere I go I always call for the extradition of corrupt Nigerians to return (stolen) money.
"This woman (Alison-Madueke) has stolen so much, not less than $2.5 billion, but unfortunately, she has a generation of looters who are supporting her. This is not good," Mr Magu said.
"We are in touch with the international community, she is under protective custody, otherwise, we would have arrested her and brought her to Nigeria."
Mrs Alison-Madueke was arrested in the UK where she fled to in 2015 after the then president, Goodluck Jonathan, lost the presidential election.
She is being investigated for money laundering in the UK, an investigation Mr Magu referenced as taking too long.
In Nigeria, the EFCC has named her in various corruption trials while properties worth billions of naira have been seized from her.
A Lagos-based lawyer and civil rights activist, Inibehe Effiong, said the EFCC boss was playing to the gallery as he has refused to mention names of persons that are protecting the ex petroleum minister.
"I think Magu is just playing to the gallery, there was a time she (Mrs Alison-Madueke) wanted to return to Nigeria to face trial, the EFCC opposed that move. The question is, is the ECC saying that the U.K government is shielding the ex-minister from prosecution or who are the people?
"Magu should be specific if people are frustrating efforts to put her on trial. Let him come out clearly to mention who these people are not to make a grandstanding statement in the media.
"The EFCC needs to understand that when they make comments like this, a large section of the country does not have confidence in what they say."
He said Nigeria and the UK government have a legal treaty that the EFCC boss could leverage on in extraditing Mrs Alison-Madueke for prosecution in Nigeria.
"There is a mutual legal treaty between Nigeria and the U.K government. Has the treaty been revoked? Has Nigeria invoked the provisions of that treaty to demand that Diezani be extradited to the country for trial, and has the attorney general of the federation activated that process? What is the position of the AGF on the matter? He should also tell us explicitly why the UK government is footdragging on extraditing the woman to the country.
"It is not a matter of saying there are people frustrating the process of bringing the woman back to the country, there is a procedure under the law, have both the EFCC and the AGF activated such procedures?"
When PREMIUM TIMES contacted the spokesperson to the AGF, Umar Gwandu, on what the office of the AGF was doing in extraditing Mrs Alison-Madueke, he first directed the question back to the EFCC chief. When our reporter insisted on knowing what the office of the AGF had done in assisting the commission, he asked for time to review the questions because he was in a meeting.
He was yet to respond at the time of this report.