The Senegalese is suspected of turning a blind eye to doping cases, notably involving Russian athletes, in exchange for money.
Investigators also suspect him of making cash payments totalling 140,000 euros ($152,000) to Gabriel Dolle, a doctor for the IAAF until last year who has also been charged with corruption, the source close to the inquiry told AFP
Diack, 82, denies making the payments. He has already been charged with corruption and money laundering.