Police are expected to descend on media organisations today in pursuit of material related to the "teapot tape", while Prime Minister John Key digs his heels in and stands by allegedly defamatory statements about cameraman Bradley Ambrose.
Among material police are looking for is documentation on whether Ambrose was paid for handing over the recording of a conversation between Mr Key and Act's John Banks to the Herald on Sunday.
The New Zealand Herald's Auckland premises - which includes the Herald, Herald on Sunday and Herald Online - is one of four outlets to be served with police search warrants.
These can be executed any time within a month of November 18.
The others are TV3, Television New Zealand and Radio New Zealand.
Police intended to execute the search warrants around mid-morning today - although TV3 has been told a search will not take place until after the court hearing tomorrow on whether the conversation was private.
Police are to meet Radio NZ staff today to discuss the warrant and the station's intention not to divulge information that may jeopardise its sources.
The warrants are part of an investigation sparked by a complaint from Mr Key alleging that the recording was illegally obtained.
The tape dominated the political landscape last week, sidelining the parties' campaigns and putting Mr Key's political judgment and the future of the Act Party in the spotlight.
Yesterday, Mr Key stood by his claim that it was a private communication, which would make it illegal to intentionally record. And he said he had no intention of apologising to Ambrose for comments that Ambrose has called "highly defamatory".
On Friday Ambrose's lawyers sent a letter to representatives of Mr Key, senior minister Steven Joyce and the National Party requesting a public retraction and apology for comments that they claim have damaged Ambrose's professional reputation.
Comments outlined in the letter include claims of criminal and unethical behaviour, and comparisons to the News of the World.
It noted that any apology would not remove Ambrose's right to start defamation proceedings.
Yesterday, Mr Key said he was "not in the slightest" concerned about possible defamation action.
Tomorrow the High Court will hear a case that the meeting was not a private communication; if the court rules it was not, the recording would not be illegal.
Mr Key said he would abide by the court ruling.
Radio NZ head of news Don Rood said station representatives would meet police today. "We protect our sources and won't divulge any information that will identify them."
The tape has derailed Act's election campaign, and has also left it at the mercy of how Epsom voters judge the importance of the tape. Mr Banks is alleged to have called Dr Brash a "strange fellow" and discussed number two on the list Catherine Isaac as a future party leader.
Mr Banks has assured Dr Brash he said nothing embarrassing about him on the tape.
If he is seen to have undermined and misled Dr Brash, the party would find it difficult to win over voters in the final week to election day.
Television NZ: Field footage of the meeting.
TV3: All the footage obtained by four cameras at the event, and all copies of the recording including transcripts.
Radio NZ: Transcripts of the original unedited interview with Bradley Ambrose on Nov 14 and supporting documentation.
Herald/Herald on Sunday/Herald online: All copies and transcripts of teapot tape, contract documentation and contact information for Ambrose, any pay information from Nov 1 to Nov 17 relating to receiving the teapot tape.