Police fear that the missing two year-old Aisling Symes has been abducted.

Inspector Gary Davey said police have begun interviewing and profiling people that they have "concerns about" in the area where Aisling went missing on Monday.

Mr Davey said police were also looking at reports of suspicious activity in the area of west Auckland over the last few weeks.

Asked what suspicious activity had been reported, Mr Davey said he would not comment.

When Aisling first disappeared, police treated it as a missing person's case but have now beefed up the criminal investigation.

"It would be fair to say, given the width and thoroughness of the investigation and given her age and how far she could move under her own steam, it would be a fair assessment that the level of investigation is increasing," Mr Davey said.

"Police must turn their mind more and more to the possibility that she has been abducted," he said.

But he said there was still no evidence of foul play and police were keeping an open mind to all possible causes of her disappearance.

"We've had a couple of calls from people who have heard a child's voice and we're following up enquiries and doing searches to find out if that's the case."

Mr Davey said there had been a number of calls from the public as a result of media attention but there have been no further confirmed sightings of Aisling and the Asian woman who was the last to see her has not yet come forward.

Police believe the woman, who was seen with Aisling moments before she disappeared, might hold the key to her whereabouts.

The woman is described as being in her mid-30s, of medium height and build, with a black top and three-quarter pants, and was accompanied by a black and grey dog.

Mr Davey said morale in the police search and rescue team was still strong despite finding no signs of the two-year-old or any items of her clothing.

He said police have been talking to the family about Aisling's habits and have learned that she loves water.

"My concern is that as time goes on and there are no more positive sightings of Aisling, that the possibility of her wandering too much further is slim," Mr Davey said.

He said the immediate area where Aisling went missing has been searched twice and police were widening their search.

Air Force personnel have been called in to help with the ground search, which was today widened to include more nearby roads.

Aucklanders young and old yesterday searched for the toddler, who disappeared from her deceased grandparents' vacant Henderson home about 5pm on a bitterly cold Monday.

More than 100 police and volunteers spent a fruitless day searching streets, creeks and inlets.

Police divers trawled the Huruhuru Creek and Taikata Inlet, focusing on a small stream behind Longburn Rd.

The Symes family were last night at their Massey home, praying for a miracle.

Cherie Tahitahi, who lives next to the house from which Aisling went missing, was outside smoking when she heard Mrs Symes shout out, about 5pm on Monday.

"I asked 'What's the matter?' and she said 'Aisling's missing'."

She said the young mother was panicking and had not thought to phone the police. Mrs Tahitahi, her husband Darren and their sons Jarrod, 9, and Troy, 7, started searching.

That afternoon Mrs Tahitahi had heard Aisling and her sister, Caitlin, giggling at ducklings at the back of the house while their mother cleaned.

It all happened very quickly, she said.

"She turned her back for like a minute and the little one was gone," said Mrs Tahitahi.

Yesterday Aucklanders came in wet-weather gear and boots to help search.

Jeremy and Betty-Ann Clough were with their children Braeden, 7, Leighton, 6, Mikayla, 4, and Caleb, 6 months - backpacks and stroller in tow.

"People need to be reminded of how easily it can happen," said Mr Clough.

At either end of Longburn Rd, police were stopping cars and handing out fliers with pictures of the little girl.

The split-level house with the daisy-dotted lawn, where she was last seen, was closed and empty.

Police have established a phone line for the inquiry - 08004AISLING (0800 4247-5464).