Sources said Air Marshal (retd) Nayyar was questioned by ED investigators for over eight hours as they also recorded his statement under the Prevention of Money Laundering Act (PMLA).
Nayyar did not talk to the waiting media after he emerged from the ED office here.
Sources said he "denied any wrongdoing in the entire deal as he said he was not in-charge of the procurement division of the IAF which handles new acquisitions."
The agency had summoned Nayyar as it had detected that the retired top IAF commander had got some funds allegedly from European middlemen and an accused in the case Christian Michel James.
They said the agency had tracked these payments being made by Michel to Nayyar and his junior, a Group Captain rank officer, as "personal unexplained payments" which includes reimbursements made in connection with some foreign travels.
ED suspects the money received in a private consultancy firm floated by the former IAF officer had links to "kickbacks" paid by the Italian firm to crack the Rs 3,600 crore deal.
