The New Zealand girl repeatedly mistaken for missing British girl Madeleine McCann has given police a sample of her DNA which will be sent to Scotland Yard.

The DNA sample is a conclusive way of proving her identity, says Detective Senior Sergeant Kallum Croudis of Dunedin police.

"The results of this process will not be known for some time," he told the Southland Times.

Police launched a five-day investigation last month when a Queenstown retailer became suspicious of a man and a young girl, who bore a resemblance to Madeleine.

However, they said they were "absolutely satisfied" she was not Madeleine, and it was not the first time she had been mistaken for the missing girl.

The girl has not been named but apparently has a similar eye defect to Madeleine.

Madeleine was nearly four when she vanished from her family's Portuguese holiday apartment on May 3, 2007 as her parents dined at a nearby restaurant with friends.

Madeleine's parents, Gerry and Kate McCann, have never abandoned their high-profile campaign to find their eldest daughter, who would now be nine.

There have been previous reported sightings of Madeleine in Dunedin, Milton, Alexandra and Queenstown. Sightings have also been reported in Sweden, Belgium, India and Australia.