Department of Conservation spokeswoman Abigail Monteith confirmed the deaths of five kiwi were being investigated.
Details were still limited but the birds' injuries were consistent with a dog attack.
The department was saddened by the deaths, she said.
Monteith said dog owners had a responsibility to keep their pets under control at all times in areas where wild kiwi lived.
''All dogs, no matter the age, gender and size, are capable of crushing the delicate bodies and organs of baby and adult kiwi. And by killing breeding adult kiwi, dogs threaten the future existence of our national icon, which is already in serious decline,'' she said.
Far North District Council environmental services manager Rochelle Deane said animal control staff were called by DoC around June 24 to collect and hold a dog on their behalf while they investigated a number of kiwi deaths.
DoC rangers had caught the dog straying in the Ōkaihau area and had taken a DNA swab.
Deane said DNA tests generally took about two weeks.
''If the results show the dog is responsible for kiwi attacks, it will be up to DoC to decide how to proceed and the dog will be transferred to the department's custody,'' she said.
The Signals Rd kiwi deaths are the worst since February 2018 when dogs killed at least six kiwi over several days on Hansen Rd, on the Purerua Peninsula in the northern Bay of Islands.
Purerua has one of the highest populations of North Island brown kiwi in the country.
In the wake of that attack, DoC took DNA samples from 16 dogs at two properties on Hansen Rd and tried to match them to dog saliva found on the dead kiwi.
DNA from one dog was a perfect match on one bird but the other saliva samples had degraded, making the results inconclusive. As a result, the prosecution had to be abandoned.
Documents obtained by the Advocate under the Official Information Act suggested the dog owner had been uncooperative, preventing DoC rangers from being present while saliva samples were collected from the dogs.
In winter 2015 at least eight kiwi were killed by dogs in the Inlet Rd-Wharau Rd area east of Kerikeri. Most of the deaths occurred near Quinces Landing but a few were close to Wharau Bay.
In that case, DoC and the FNDC worked together to identify dogs owned by three residents.
Two of the dogs were surrendered while the owner of the third said he had put the dog down himself. Two owners were fined $200 for failing to keep their dogs under control.
Vehicles also take a toll on the national bird with at least seven killed by cars in the Rangitane-Opito Bay area, north of Kerikeri, in 2019. Another three were killed on Opito Bay Rd in the space of a week in January this year.
The worst known loss of kiwi anywhere in New Zealand occurred in the Waitangi Forest, between Kerikeri and Paihia, in 1987 when a single dog dumped in the bush killed an estimated 500 kiwi. By the time the dog was caught, it had been living off the ground-dwelling birds for six weeks.
The official conservation status of the North Island brown kiwi is "declining".