"We're looking at top of Boulcott, along the Terrace, the Plimmer Steps area, and on the bottom of Boulcott on Willis and Lambton Quay."
Mr Miller said CCTV footage reviewed so far had shown at least two people and three vehicles were in the area around the time of the attack.
"We believe that probably around 5.30 a male and female walking up Boulcott St. We picked that up [on CCTV] on one end of Boulcott St. We don't know if they have seen anything, but it is extremely important if that was you to get hold of police."
Mr Miller said the pair were "definitely witnesses" which could assist inquiries, as opposed to suspects.
"They may have seen something totally unrelated to the attack, but may help us greatly piecing it together.
"Also we have a courier van which we haven't identified the company, which we believe was driving up Boulcott St, we have a taxi and we have a third vehicle, at the moment we can't identify that vehicle."
Mr Miller said neither Mr Cottrell's wallet or any of its contents have yet been located.
He said police still had confidence in finding the journalist's attackers.
"This is what the police call a 'who-done-it' homicide. It's a random attack ... the person or persons that he has come into contact with have nothing to do with him. So we don't have a starting point like we do in many inquiries where he may have known or had some association [with the attacker].
"There is a good chance whoever has done this attack would have told someone.
"There's someone out there who will know something from these people and they need to get hold of us immediately."
- Herald Online Staff