The woman assaulted in an incident in Massey this morning is expected to undergo surgery at Auckland Hospital today.
The woman, aged in her mid-40s and of Chinese descent, is now in a stable condition at Auckland Hospital, detective senior sergeant James Bothamley said today.
Police had spoken to her "very briefly" but would not be releasing details of what she said, he told a media conference outside the scene this afternoon.
She had fled to a neighbour's house with serious head injuries following the assault.
The woman was due to undergo surgery for her injuries later today.
"At this point we believe the incident is domestic-related. The body in a lower part of the address is the male partner of the female who was assautled," Mr Bothamley said.
"At this point in time we are not seeking anybody else in relation to this incident."
Neighbours reported a large explosion coming from the property this morning.
Firefighters found a male body in the downstairs garage at the house. It is believed a number of painting supplies and other flammable materials were the likely fuel to the fire.
It isn't yet known how the fire started, Mr Bothamley said.
"The investigation is in its early stages, fire scenes are notoriously complex to investigate and it will be sometime before we know exactly what took place in the lower part of the house."
Witnesses to the assault are being spoken to, Mr Bothamley said.
The circumstances surrounding the man's death were still unknown.
"At this stage what we have is a body in a garage and we're still investigating it."
The man was also aged in his 40s and of Chinese descent. The pair lived at the property where the fire took place and are believed to have adult children from previous relationships who do not reside at the home.
Police had received no previous calls for domestic-related incidents to the home.