A thorough police search of the Waikato River has produced no "significant" clues for investigators, who continue their hunt for Hamilton man George Taiaroa's killer.
Mr Taiaroa, 67, was farewelled at a funeral in Levin during the weekend after being shot in the head last Tuesday while manning a stop-go sign on Tram Rd, near Atiamuri.
Police said the Police National Dive Squad, who started a search of the Waikato River on Friday near Tram Rd, had completed their search and "nothing of significance had been located".
They also said they received 25 to 30 calls from the public during the weekend on a newly set up 0800 number, for calls relating to the case.
Police said it was still too early to determine a motive for the shooting and their main focus was locating a blue 4WD vehicle, possibly a Jeep Cherokee, which was seen leaving the murder scene.
Any information on the case, including sightings of a blue 4WD vehicle on Tuesday, can be passed onto police by calling 0800 Kingswood (0800 546 479).
"We really want to hear from anybody who may have seen that vehicle," Detective Inspector Mark Loper said on Friday.
"I also want to appeal directly to the driver of that vehicle to come forward. Likewise anyone who knows or suspects who killed Mr Taiaroa."
Meanwhile, rumours have started to circulate about the motives behind the fatal shooting. One report said the murder was part of a vengeance killing after Mr Taiaroa helped put a man in jail about 10 years ago.
Police are also now hoping to talk to everyone who travelled over the one lane bridge on Tram Road in the hour leading up to the shooting.
Police believe that motorists who passed over the bridge between 2.30pm and the fatal shooting may have information they don't realise is important to the inquiry.
Mr Loper said the information those drivers could provide could be crucial in piecing together events leading up to the shooting.
"They may not think they have anything useful to offer but the slightest snippet of information might be invaluable to the investigation; particularly in terms of the people and vehicles they saw as they passed through," he said.
"We don't know how many vehicles travelled through during those 30 minutes but we do know that at one point a two tone green vehicle came nose to nose with a tractor on the bridge and had to reverse up due to a miscommunication at the traffic control. We are keen to speak with that potential witness and any others who crossed the bridge."
Mr Loper said police also want to speak to anyone who stopped at the scene or passed by after the shooting who hadn't yet spoken to police.
Another focus of the investigation is to identify any security footage that may be of assistance.
"We know that commercial trucks often have cameras mounted on their cabs. Although we are liaising with companies that travel the area we know that some trucks with cameras may be privately owned," Mr Loper said.
"We also know that farmers and other rural residents often have cameras installed to help protect their properties. The vehicle we are seeking will have off-road capability so just because a camera isn't on the road doesn't mean it won't be useful. We would encourage everyone in and around Atiamuri to check their cameras."
Anyone with information is asked to contact the investigation team directly on 0800 Kingswood (0800 546 479). Alternatively information can be provided anonymously via Crimestoppers on 0800 555111.
Today marks day seven of the murder investigation.