MARILYN Wallman's family has renewed pleas for information about the teenager's death.
A 14-year-old Marilyn disappeared on March 21, 1972 near Wallmans and Eimeo roads on her way to catch the school bus.
After a 45-year investigation with periods of hot breakthroughs, manhunts and excavating backyards the person or people who killed Marilyn remains unknown.
The recent death of Marilyn's uncle Tony has brought fresh fears into the minds of the family, that they and those that may know what happened to her could die before the truth is revealed.
Mackay Criminal Investigation Branch officer-in-charge senior sergeant Dave Tucker said police believe someone knows what happened to Marilyn and they should come forward before it's too late.
"One of the key parts of the investigation has been the Holden sedan that was seen around Wallmans Rd around the time Marilyn went missing," he said.
"We have done a lot of work on that particular vehicle over the past couple years. We have identified fresh witnesses as well.
"This is part of our fresh appeal because we have identified fresh witnesses who weren't involved in the incident but had seen the vehicle. And they have confirmed we're looking at the right vehicle."
He also said the $250,000 reward from Queensland Police was on offer for information that lead to an apprehension and conviction.
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