"I believe it is misadventure but I can't rule out any other possibilities at this stage," Inquiry head Inspector Gary Davey said today.
The two-year-old disappeared from a house in Longburn Rd in the Auckland suburb of Henderson on Monday last week, sparking an intense search.
After an initial search of the area police then said it was highly likely she had been abducted but said all their inquiries were producing nothing positive.
They reviewed their search and last night dug up a drain at the back of a house near where she was last seen and found her body.
The body was found in the drain 1.5 metres underground and 36m from a manhole covering an entrance to it.
Inspector Davey told media today the drain that had been inspected several times, the first time within minutes of the first police officer arriving at the house after Aisling was reported missing.
Mr Davey said it was unlikely she could have been saved if police had done anything different.
"I believe the police on the night did everything they could to find her and I am also sure we would not have been able to save her, even at that point."
He said the search team had kept an open mind about Aisling's disappearance and that was part of the reason they found her body.
"It is still too early to say exactly how Aisling has got into the drain or how long she had been there."
Mr Davey said she was probably in the drain when the first police officer had a look but had moved further down than he could see.
"He used his torch down the drain but was unable to see or hear anything which would indicate that she was in there...at that stage she had moved down past that.
"As we know all drains face downhill and it would have been impossible for her to turn around if she was crawling.
"It was raining at the time. There was water flowing in the drain and whether that was washing her down or whether she was crawling down we simply do not know."
Mr Davey said he believed her death was probably an accident.
"It is more likely than not that she had been there from the start.
"I believe it is misadventure but I can't rule out any other possibilities at this stage."
He said the scene was being treated as a crime scene and until police knew more through the post mortem and other inquiries they needed to keep an open mind.
He said the Asian woman police had earlier said was a crucial part of the case was identified last night and was still being sought.
"We would still like to speak to her.'
When police were first called to the Longburn Rd house on Monday last week a police officer searched the pipe three times, Mr Davey said.
The manhole cover was ajar about 10cm and the first police officer looked down the pipe and there was no sign of a body.
"He called out and did not hear anything other than running water,' Mr Davey said.
The officer then searched towards the stream and 15 minutes later returned to the manhole, climbed about two metres down the larger access pipe after moving the manhole cover back.
He shone his torch down the smaller 375mm drain at the bottom and could see nothing. He also called her name but there was no response.
"He believed he could see five metres up into the drain and five metres down the drain."
The drain was searched for a third time later in the night by search and rescue searchers, Mr Davey said.
During the search Aisling's father Alan Symes also climbed down the pipe and looked for his daughter, said Mr Davey.
He said the manhole cover was about 600mm wide and weighed about 20kg, something well beyond the capacity of a child to move.
He said part of the police inquiry would be to establish how Aisling got into the drain.
Mr Davey said when the search was reviewed this week a decision was made to use specialist techniques to search the drain and the camera probe was put down.
"We searched both ends of that drain with cameras. Even as a result of that camera search we were still unable to locate or identify Aisling."
The drain had a history of blockages and the decision was then made to dig up the drain, Mr Davey said.
After five hours of digging and using concrete cutters they reached the drain.
"Unfortunately, once we did cut open the drain we were able to see Aisling," he said.
He said he had visited the family and they were distraught.
At a press conference at Henderson police station this morning Inspector Davey referred to the body as "Aisling" though identification is yet to be carried out.
Her family was reported today to be "absolutely distraught" their church pastor Russell Watts said.
It was a "very, very caring, extended family who are all very upset," he told Radio New Zealand .
He said everybody had shown the family exceptional support but now they needed a bit of space.
Messages of support and sympathy and gifts for the family could be dropped at the Ranui Baptist Church to be taken to the family.
Aisling (2) disappeared on Monday last week.
After a search police said they thought she may have been abducted. They appealed for information on an Asian woman seen walking her dog about the time she disappeared shortly after 5pm but she was never found.
After a week of intense searching, police found the body about 8pm last night and it was removed from the drainpipe about midnight and taken to the mortuary at Auckland Hospital for a post mortem.
In Henderson today police stood guard on the Pomaria Rd house where the body was found.
They were kept supplied with hot drinks by local residents and candles burned outside the property throughout the night.
Last night several hundred people gathered in Pomaria Rd, mostly quietly reflecting and offering unspoken support for the family.
The discovery of the body was announced last night by a visibly upset inquiry head, Inspector Gary Davey, the man in charge of the week long search for Aisling.
He said it was with "tremendous sorrow" that he was announcing the discovery of the body.
At one stage at the hastily called media conference last night, he stopped to gather his emotions before he continued.
The news of the disappearance of the little girl, described as a bright and bubbly toddler, has attracted worldwide interest.
Aisling's father is from Ireland and the Irish news media has followed the case closely.
A facebook website called Find Aisling Symes had 20,995 members.
Waitakere Mayor Bob Harvey said the only way Aisling could have got into the drain was through a manhole cover.
The cover was somehow put back over the hole after the toddler went through it, he told TVNZ's Breakfast programme.
"The drain goes down into a very narrow pipe -- about 15 inches across -- and it's full of weeds and roots of a massive, massive willow and that's where her body came to rest before it keeps going and connecting with other pipes."
The area where the body was found has been cordoned off and was being treated as a crime scene.
It was not known how long the body had been in the drain, nor how it had got there.
