Abuja - Nigeria's former highest-ranking airforce officer is being questioned as part of an investigation into the alleged diversion of funds intended to fight Boko Haram, a source close to the probe said on Thursday.
"Former chief of air staff Air Marshal Adesola Amosun has been with us since yesterday [Wednesday]," the official at the Economic and Financial Crimes Commission told AFP on condition of anonymity.
"He is being interrogated in connection with the arms deal scandal."
A statement from President Muhammadu Buhari's office on January 15 said the EFCC probe into alleged weapons procurement fraud had been widened to include 17 former or serving high-ranking officers.
They included the former chief of defence staff, Alex Badeh, whom Buhari replaced last year, it added.
The probe would look at "the roles of the officers and the... companies and their directors in fundamental breaches associated with the procurements" by former national security advisor Sambo Dasuki and the air force, the statement read.
Dasuki is facing a string of allegations over allegedly bogus arms deals to provide Nigeria's military with the weapons and equipment needed to fight the Islamist group in the country's northeast.
The materiel either never materialised, was over-priced or deficient, according to a panel looking into the procurement.
Prosecutors allege the money was channelled to the then-ruling Peoples Democratic Party (PDP) to fund Goodluck Jonathan's re-election campaign last year.
Jonathan lost to Buhari, a no-nonsense anti-corruption campaigner and former military ruler, in the first democratic transition of power between political parties in Nigeria's history.
Buhari has embarked on a wide-ranging crackdown on endemic graft since taking office last year, leading to a slew of arrests and charges, particularly against senior PDP members and supporters.