A $250,000 reward is now being offered for information about the disappearance of Helen Munnings.
The 20-year-old disappeared without a trace on July 23, 2008, and Burnie Police have now increased the reward from from the initial $50,000.
Police have recently begun looking into fresh leads, which has led to the decision to increase the reward.
"Investigators have long held the view that there are people in the community who have knowledge of Helen's disappearance who, for whatever reason, have not either been able to come forward or have been unwilling," Western District Commander Debbie Williams said.
"This reward may well serve as the driving factor to motivate them to speak with police."
Anyone with information that could assist the police investigation is asked to contact Police on 131 444 or Crime Stoppers on 1800 333 000 or online at crimestopperstas.com.au.
The pregnant mother was last seen walking near the Burnie paper mill on the Bass Highway in 2008.
She left behind a two-year-old son, and in 2012 Coroner Robert Pearce found she was most likely dead.
Coroner Pearce could not rule out murder or suicide, but said there was not sufficient evidence to find either of those scenarios to be the case.
He found Ms Munnings died on or around the date she was last seen, in the Burnie area.
"Helen was beautiful and she adored her son," her mother, Karel Black, said in 2017.
"She loved him. Everyone thought Helen was nice. She was too nice."
Last year, Ms Munnings' former partner and father of their child Donovan, Adam Taylor spoke to The Advocate about her disappearance.
Mr Taylor was allegedly the last person to see Ms Munnings, but Coroner Pearce's 2012 findings could not establish any evidence that he, or any other person, had contributed to her death.
Despite the coroner's findings, Mr Taylor said people continued to ask him about Ms Munnings' on an "almost daily" basis.
