It is understood a family member was driving the car that reversed into the boy in the driveway of a house on Eastburn St. The 3-year-old lives at the home with his parents and four older siblings.
Inspector Kay Lane told the Herald on Sunday it was an awful situation and said the Serious Crash Unit was investigating.
New Zealand has a high rate of children's driveways deaths and injuries.
A child was seriously injured by a vehicle driving on a private driveway in New Zealand every fortnight, it has been reported. And five children were killed annually, on average.
Children aged between one and three years were most at risk.
Research had shown about 64 per cent of drivers involved were a parent. Another 15 per cent were relatives and 21 per cent were visitors.
A Safekids Aotearoa campaign supported by ACC was launched in 2015 to help reduce the rate of children's driveway deaths and injuries.
Tips to reduce the risk of driveway accidents
• Use safety gates - to help prevent children sneaking outside unnoticed
• Actively supervise children, especially before meal times - most incidents happen during busy times of the day, eg when parents are preparing meals
• Build a fenced-off play area - toddlers can move faster than we think, so having a play area separated from the driveway can help when supervision fails
• Know your blind zones - reversing cameras on cars are useful, but there are 'blind zones' in front, behind and along the side of your car that you need to check
• Be aware of the risks - your driveway is risky if, for example, you live in a busy home with lots of cars, have a shared driveway, or the driveway is the only pedestrian pathway to the house