"As in all police investigations we have to take all reasonable and practicable steps to find people and information that will help our inquiries.''
Meanwhile, Mr Hooper said police were aware that the recording had been leaked on the internet today.
This would be factored into the investigation, he said.
Prime Minister John Key today apologised to older New Zealanders if they were offended by his comments caught on the tape, which were alluded to by New Zealand First leader Winston Peters before the election.
But Mr Key said he had not listened to the tape himself, and maintained the contents of the conversation between him and Mr Banks were "pretty bland''.
"Older New Zealanders at some point pass away, and it's a statement of fact that Winston Peters' base has typically been represented by older New Zealanders,'' Mr Key said.
"But that was a private conversation. I would always phrase things in a better way if it was a public conversation.
"So if there was offence, yes I would apologise for that, but I haven't listened to the tape.''
Meanwhile, Mr Key will now have to change his mobile number in the wake of the tape's release.
Mr Key gave Mr Banks his cellphone number during the media stunt and that has now been shared via the web release of the conversation.
He said today that a previous experience of having his cellphone number become widely available meant he would have to change it.
Mr Key, who is in Auckland giving his first major speech of the year, said he would phrase things differently in public than in private.
He said he would listen to it in "due course".
He said the leaker may have broken the law, but that was a matter for police.
"[Publishing the tape] is not something I've authorised, so anyone that's done that may find themselves in breach of the law."
Labour leader David Shearer said there was "nothing surprising'' in the tape, but he criticised Mr Key for laying a complaint with police.
"There was nothing [on the tape] that really made a real difference. Why do we have to pull the police in to stifle comment coming out of our four largest media organisations? I think that's nonsense.
"His bringing in the police was completely heavy handed, completely unnecessary given the content of the tapes.
"He overreacted. I think he did not really want it to get out before the election, and therefore he took the unusual step of bringing in the police .... when police have much better things to do."
Mr Peters this afternoon called for Mr Key to withdraw his police complaint.
"Going to the police about this tape was a pathetic political stunt aimed at shutting down discussion of an election blooper and Mr Key should be ashamed of himself," Mr Peters said.
Earlier today media and politicians, including those in the Labour Party, were notified that the recording had been uploaded onto a website.
The timing of the leak means that the teapot tape is likely to become a focus when parliament sits for the first time this year on February 7.
A URL on the webpage is accompanied with an invitation to download the tape "so that it can't be taken back".
After the cafe meeting, Mr Ambrose passed a copy of the recording to the Herald on Sunday, which asked Mr Key's permission to publish it.
He declined and laid a complaint with police, calling the recording deliberate and UK style News of the World tactics.
Mr Ambrose responded, saying his professional reputation had been tarnished and he took a case to the High Court seeking a declaration about whether the conversation was public or private.
If the court had ruled it a public conversation, it could not have been illegally recorded.
But the court declined to rule of the conversation's status, saying it would undermine the ongoing police investigation.
Police then descended on four media outlets to seize material relating to the investigation.
A police spokesman said that investigation - dubbed Operation Carlton - was still continuing.
It is being lead by two officers based in Glen Innes, who are currently seeking interviews with those who were at the cafe at the time.
