A police dive squad has been brought in to help in the search for a missing west Auckland toddler.

Two-year-old Aisling Symes went missing from Longburn Rd in Henderson around 5.15pm last night. She was with her parents at the time, who were cleaning up a family member's vacant home.

Around 100 searchers are looking for the little girl, including a large team of specialist rescue personnel.

Attention has now turned to the rain swollen river which runs alongside the road.

Police divers are concentrating on the waterways in the Huruhuru Creek and Taikata Inlet.

It was bitterly cold overnight but one theory police were working on was that she may have been taken in by a young Asian woman who may have spoken to her about the time she was last seen.

Inspector Gary Davey said the woman may not speak English well and may simply not understand the fuss the little girl's disappearance would have created.

The woman is described as being in her thirties, approximately 1.65 metres tall and of medium build.

She was wearing a black top with three-quarter length sleeves and had long black hair.

The woman is also described as having a black and grey dog on a lead.

Mr Davey said it was unusual that if someone had taken Aisling in for the night that they had not called police.

"If one of the neighbours had picked her up and was looking after her we would have expected them to have called us by now."

He said they were probably now past the point she may have spent the night asleep in a warm place.

"From about 9am or 10am our level of concern has been increasing steadily."

He said the family was very distraught. Victim support counsellors and the police chaplain were with the family.

"They are terribly upset but they do have a lot of support."

Police spokesman Kevin Loughlin earlier said foul play was not being considered by police.

Mr Loughlin requested residents of Longburn Rd, Kingdale Rd and Rathgar Rd to check their properties for Asiling, particularly sheds, out buildings, fencelines or other places that a small child may explore or hide in.

Aisling was described as being tall for her age, of European appearance, with light brown hair.

She was believed to be wearing a green jacket or ski jacket, blue jeans embroidered with flowers, and white tennis shoes.

Aisling's father, Allan Symes, told Radio New Zealand he was overwhelmed at the number of people who had turned out to search for his daughter.

"I would just like to say to everyone out there my heartfelt thanks and my wife Angela's heartfelt thanks to all the neighbours, the volunteers, the search teams, fire rescue who are out there who have just turned up.'

Police also thanked those who volunteered in the very bitter weather yesterday, but asked anyone wanting to assist in further searches wait for a specific request before returning.

Anyone with information about Aisling or her whereabouts was asked to contact the Henderson Police Station on 09 839-0600.