The woman was a central figure during the week-long investigation into the toddler's disappearance.
After initial searches proved fruitless, it was feared Aisling had been abducted.
Police still want to speak to the woman, despite Aisling's body having been recovered and a postmortem examination revealing she died by drowning.
The toddler was found in a stormwater pipe about 8pm on Monday, 36m from a manhole cover at 5 Longburn Rd, Henderson.
Aisling was with her mother at 7 Longburn Rd, the home of her deceased grandparents, when she disappeared.
The drain had been the subject of four complaints to the Waitakere City Council, and at least one person raised safety concerns after a build-up of water blew the manhole cover off.
The drain, which is 37.5cm wide and runs at a depth of 1.4m, feeds into Lincoln Stream behind Longburn Rd.
Police found the manhole cover dislodged during the initial search for Aisling, but weighing about 20kg it was too heavy for her to have lifted.
Police would now work on establishing how Aisling got into the drain.
Inquiry head Inspector Gary Davey yesterday said the decision to re-check the pipe was made in a review of the investigation, which was stalled.
With "other areas of the inquiry going nowhere" it was decided at the weekend the drain should be checked again, with the help of Watercare Services.
Specialist cameras with the capability to see up to 10m were brought in but did not detect the toddler's body.
As the drain had a history of blockages, it was decided to dig it up. More than 1m of soil had to be excavated and obstructions cleared before Aisling's body was found.
Insp Davey said it would have been impossible for her to turn around in the drain.
One West Auckland drainlayer - who did not want to be named - said he immediately thought about the manhole cover after hearing Aisling's body had been recovered.
He said he had raised concerns about it with the Waitakere City Council a year ago, after making a closed-circuit TV inspection of the stormwater line.
"It's an old lid that should have been replaced ages ago. When we came across that, we let the council know. They pop up in bad stormwater."
Sonya Carrington, a former tenant at 5 Longburn Rd, said the main reason she moved was "because I didn't want my kids down that drain".
Waitakere Mayor Bob Harvey last night told TV1'she was now aware of the four previous complaints, but did not know what action had been taken.
"I feel disappointed more than angry. I don't think it's a time for anger."
He was surprised the people concerned about the drain had not mentioned it to the police during the search.
Waitakere City Council spokesman Wally Thomas said a complaint was received on September 11 that the manhole cover had lifted off.
Workers found large willow-tree roots in the drain and began "the process of deciding how best to go about removing them".
Asked if that decision was made before Aisling went missing, Mr Thomas said: "No, sadly, not."
