Four media outlets, including Radio New Zealand and TVNZ, are to be searched for any material they might have in their possession that relates to the tea pot tapes.
Prime Minister John Key laid a complaint with police after his conversation with Act party candidate John Banks in Epsom last Friday was recorded by a freelance cameraman.
Illegally intercepting a private communication carries a penalty of up to two years in jail.
Under the act, a private communication is one made under circumstances that "may reasonably be taken to indicate" that the parties involved want to keep the communication to themselves.
But it does not include situations where any party in the conversation "ought reasonably to expect" that it may be intercepted with express or implied consent.
