Missing toddler Alyssa Barker found

Alyssa Barker. Photo / Supplied

An 18-month-old girl allegedly kidnapped by a woman is back at home with her family tonight.

Alyssa Barker was taken from her house near Kaukapakapa yesterday afternoon by a family acquaintance, 27-year-old Skye Mason.

The pair was last seen at a property in Glen Eden about 10pm yesterday.

Police held grave concerns about the welfare of the pair because they were lightly clad and rain and cool temperatures were forecast for tonight.

But police said tonight they had been staying with a woman in Swanson.

The woman recognised them from the television news then waited until they were asleep before calling police at 9.15pm.

Alyssa was to be reunited with her family shortly and 27-year-old Ms Mason was in police custody.

Police said Alyssa was well and didn't seem to be suffering any ill-effects as a result of her 36-hour absence from her home.

Detective Inspector Stan Brown of Waitakere police said he and his staff were delighted to be able to return Alyssa to her family and very grateful to media for their support during what was a nervous search.

"This is one story that does not have a tragic end for a child and for that, we are very happy."

Mr Brown told media earlier today that Ms Mason was known to have mental problems and Alyssa's parents took her into their home "out of the goodness of their hearts''.

When they were seen last night, police said people who saw them observed that Ms Mason was caring for Alyssa "as if she was her own child''.

Police took the unusual step of alerting the public about the kidnapping by putting information about the little girl on electronic motorway signs between Auckland and Wellington.