The teenager was missing for seven days before her partially decomposed body – naked and burnt – was discovered under sheets of corrugated iron at the abandoned Pelton Colliery, about 8km outside Cessnock.

Police have spent a quarter of a century investigating the 17-year-old’s mysterious death but her family still has no answers.

The Hunter Valley’s police commander announced on Friday the investigation had been renewed. 

Read more: More than 20 Hunter deaths in cold case review

Superintendent Chad Gillies said detectives would look “with a fresh set of eyes” at the evidence collected since the Cessnock teenager – who would now be 42-years-old – died.

“We believe there are people sitting on information or people out there who have information pertinent to the investigation who haven’t come forward at this point,” he said.

“For the family of someone who has passed away 25 years ago, time doesn’t heal those wounds. It’s a tough time for them, any time an anniversary comes around like this. 

“They deserve closure and we’re going to do our best to try to give them some answers. But again, we need the public’s assistance.”

Superintendent Gillies would not be drawn on whether police had identified any persons of interest but said detectives would be “reviewing all associates, anyone that assisted us initially”.

Read more: The Hunter’s cold cases

Allison’s family last saw her as she left home to meet friends at the Carousel Cafe in Vincent Street on the evening of October 6, 1993.

Her station wagon, with her purse inside, was found in the Cessnock Ex Servicemen’s Club carpark soon after she went missing and her clothing was discovered in a plastic bag dumped in bushland near Cessnock a year later. 

A post mortem failed to determine the cause of death.

In 1997, a jury acquitted a 28-year-old man known to Allison of deliberately concealing her body and two counts of perverting the course of justice. 

A year later, Allison’s case was included in an investigation into whether a serial killer was responsible for the death and disappearance of 10 young people in the Hunter between 1978 and 1994 – but it did not lead to answers.

At the time, police posted a $100,000 reward for information that helped solve the case – a sum still on offer.

Allison’s mother Loretta and older sister Sonia were unavailable to speak on Friday – her father Allan died in 2001 having never found out what happened to his daughter.