The German backpacker had arrived in Tasmania a few days earlier and left her pack with the bike hirer, telling him she planned to ride down the East Coast to Hobart.

On March 11 she made a phone call to her parents and travelled by bus to St Helens where she spent the night at a hostel.

That phone call was the last the devoted couple heard from their daughter.

On March 12, the 26-year-old was seen riding the hire bike four kilometres south of Scamander, heading toward Bicheno.

And then - nothing.

A coronial inquest, 19 years of investigation and a string of tip-offs from the public later and still no hard evidence has been unearthed to say what happened to Miss Grunwaldt.

Her death has been narrowed down to a day - March 12, 1993 - and an area between St Helens and Bicheno.

But not a trace was left to tell how she died.

Information that led to the excavation of the Bicheno tip yesterday is the strongest lead in the case in years.

If the bike is uncovered at the tip, it will bring closure one step closer for a grieving family.

``As we stand here today we're still not sure what happened to Nancy,'' Detective Inspector Scott Flude said yesterday.

He said the aim of the ongoing police investigation was to find answers for her family.

Nancy's father, Bernd Grunwaldt, died in 2005 after a long illness. Friends said he had ``aged a lot over Nancy''.

Police contacted her mother, Helga, last week to tell her about the proposed excavation.

The couple visited Tasmania regularly searching for signs of their lost daughter and Mrs Grunwaldt has planned to visit Tasmania next year to mark the 20th anniversary of her daughter's disappearance.

``To be able to provide some closure to her mother would be the best outcome,'' Detective Inspector Flude said.

A 2003 coronial inquest into the disappearance did not make any conclusive findings.

Coroner Peter Wilson found there were five likely scenarios for Miss Grunwaldt's disappearance, but said that foul play was the most likely.

If not murdered, he said alternative explanations were that she was struck by a passing motorist on her bike and either fell out of the view of the road or her body and possessions were disposed of.

Mr Wilson said she could also have met her death by misadventure, such as falling down a mine shaft or drowning, with her possessions found and disposed of.

The coroner's findings strengthened the public suspicion toward homicide.

Within 18 months of Miss Grunwaldt's disappearance, the East Coast faced another chilling mystery.

In October 1995 a walker discovered the mutilated body of Italian law student Victoria Cafasso on a Beaumaris beach.

Miss Cafasso had been stabbed 17 times in the face, head, back and chest.

Her body was discovered by a woman walking her dog on October 11, just an hour after she was believed to be murdered.

The frenzied attack, coming so soon after the disappearance of Miss Grunwaldt, sparked fears of a serial killer roaming the East Coast.

But last year retired detective Bob Coad said that, in Miss Grunwaldt's case at least, there was a less sinister explanation.

``Nancy Grunwaldt was not murdered,'' Mr Coad told The Examiner.

``Her death was the result of a tragic accident - and now it's time for the person responsible to come forward.''

In the exclusive interview, Mr Coad rejected the coroner's finding.

He said that in the first months of the investigation a Hobart solicitor reported a disturbing phone message from around the time of Miss Grunwaldt's disappearance, in which a distraught male caller said he had hit a cyclist on the East Coast and needed help.

But by the time detectives visited the solicitor, the answering-machine tape had been recorded over.

Anyone with information about Nancy Grunwaldt is asked to call Crime Stoppers on 1800 333 000.

There is a reward for information offered through Crime Stoppers.