Police have launched a murder investigation after revealing the identity of the mystery Port Waikato skeleton as that of teen Jane Furlong.

Furlong, 17, went missing from Auckland's Karangahape Rd in 1993 and her family thought she would never be found.

When she disappeared, Furlong was due to testify as a witness for the prosecution in two separate cases - one involved gang members accused of an assault, the other a businessman charged with brutal attacks on sex workers.

She was preparing for her court appearance with police the day before she died.

Her remains were found on Sunset Beach last month by a woman walking her dog. Police narrowed down their search to 30 females aged 15 to 25 years old who had been missing for more than a decade, then used DNA testing to identify her.

Detective Inspector Mark Benefield confirmed police had been running a homicide investigation since the skeleton had been discovered.

"Police have always believed she disappeared in suspicious circumstances and, while it brings little comfort to know the initial concerns about her wellbeing were well-founded, it's pleasing that we have some evidence to work with in terms of our current homicide investigation.

"Over the past few weeks since what we thought could be Jane's remains emerged from the sand dunes on Sunset Beach, we've carried out a number of inquiries and have a plan in place for how this investigation will progress.

"Central to that plan is information. We need information from anyone who, over the past 19 years, has been living with the knowledge that Jane was killed and buried in a lonely and cold sandy grave," Benefield said.

Police had informed Furlong's mother and son - who was an infant when she went missing - that they had identified her.

Warwick Furlong, Jane's uncle, was overseas when his niece went missing and did not know her well but said the family did not think police would ever find her.

"We didn't really think that anything would ever happen. She'd gone and that was it."

One of his sisters told him several weeks ago a skeleton had been discovered and that it was Jane but he had not heard any further details until today.

His brother, Michael - Jane Furlong's father - who died last year, never talked about her disappearance, he said.

Benefield said since Furlong went missing police had carried out hundreds of inquiries during two main investigation phases, the first in 1993 and then again in 1996.

A 2007 television programme that featured clairvoyants also sparked some further inquiries.

He said the latest probe was "well underway", with some well-preserved items associated with Furlong's skeleton recovered.

Anyone with information can call 0800 675 263 or email furlong@police.govt.nz.

- © Fairfax NZ News