A security guard was tonight watching over the Taita Drive property in Taita where the baby was found wrapped in a towel about 10.30am.
Taita Drive resident Maria Tagoai said her neighbour, a woman in her 50s, saw the dead baby wrapped in a towel when she went to hang out the washing this morning.
Ms Tagoai said the woman and her husband, who was at work at the time, were staying with family tonight after the discovery.
Inspector Shane Cotter said the woman was shocked and distressed at the discovery.
"Our biggest concern at this time is the health and well-being of the mother of this baby girl and whether or not she has received any immediate medical attention post birth," he said.
The baby looked to be no more than 24 hours old.
"A post-mortem examination will be carried out on Wednesday morning. This will help determine if she was alive at the time of her birth or not," Mr Cotter said.
"Our priority right now is on finding the mother of this wee girl and ensuring she does not have any medical complications as a result of the birth. I appeal to this woman to come forward and speak with us as soon as possible," Mr Cotter said.
Often in such cases, a mother has concealed a pregnancy from family and friends.
"We appeal to anyone who may know a woman in the Hutt Valley area who has been large and lost a significant amount of weight in the past couple of days. It's important this woman receives the medical attention she requires as soon as possible," he said.