Zaken has been suspended from her job for six months while police conduct their investigation.
"The prime minister gave testimony today to police concerning his period of minister of finance," an official in Olmert's office said, speaking on condition of anonymity.
Olmert served as finance minister before becoming prime minister in January last year.
During his long political career, Olmert has been dogged by allegations of corruption, but never charged.
Currently, police are investigating his property dealings and his role in the government's sale of a majority interest in a bank while he was finance minister in 2005.
Olmert's finance minister has been accused of embezzlement and his justice minister resigned and was convicted of sexual misconduct for forcibly kissing a young female soldier.
During a recent interview, Olmert complained that he felt that he and his associates were being hounded by a "platoon of investigators".