DoC Bay of Islands manager Rolien Elliot said the deaths came as a surprise because Purerua residents were passionate about wildlife and normally kept their dogs under control. That led DoC staff to believe it could be a new dog in the area.
Council animal control staff and DoC rangers went door-knocking in the area to urge owners to keep their dogs under control at all times, especially at night.
A resident had spotted a wandering dog as he came home one evening and had been able to give a basic description.
DoC staff had taken samples of dog saliva from the dead birds as well as from nine dogs to see if the DNA matched. They were now waiting for the results of DNA analysis. Dog owners had been cooperative and "wanted to do the right thing", Ms Elliot said.
No more kiwi deaths had been reported since then.
"The first kiwi was a huge female, which suggested she was a good breeder and had been around for some time, so that's particularly sad."
The others were two adult females, two adult males and one juvenile. Autopsies were carried out by Massey University experts who said the size and spread of incisor marks were consistent with an attack by a large dog.
Ms Elliot said the deaths reinforced the importance of keeping dogs under control in kiwi areas, especially when moving to a new area. It was also important to make sure any visitors with dogs got the message.
In winter 2015 at least eight kiwi were killed by dogs on Wharau Rd and Inlet Rd in Kerikeri. In that case DNA testing identified a bull mastiff bitch as responsible for at least some of the deaths. Two other dogs at the same property were thought to have been involved.
One dog was put down by its owner before it could be impounded. The second was put down by council staff while the third died in the pound.
The two owners were each fined $200 for failing to keep a dog under control. However, the Dog Control Act allows for fines up to $20,000 or a maximum of three years' jail for owning a dog that causes serious injury to a person or kills protected wildlife.
Once the Purerua investigation is complete the carcasses will be given to local hapu Ngati Torehina. Kaumatua Hugh Rihari said the pelts, feathers and bones would be used for customary purposes and teaching others how to make traditional feather cloaks.
Purerua Peninsula is known for its high numbers of kiwi. During last summer's drought a number were seen in daylight, possibly because thy were unable to find enough food in the parched ground at night.