Police believe they have already spoken to people who hold the key to solving Logan schoolgirl Tiahleigh Palmer's murder and hope a new $250,000 reward will provide the incentive to get them to talk.
Detective Superintendent Dave Hutchinson announced the reward on Monday, after the Queensland Government agreed to fund it, along with indemnity from prosecution for the first person person to provide information that leads to the conviction of Tiahleigh's killer.
He said the indemnity was particularly important, as detectives surmised they had already interviewed people who knew what happened to the 12-year-old nearly four months ago.
However, he said investigators believed they were withholding information from police, either out of fear for repercussions of their own involvement in her death or loyalty to Tiahleigh's killer.
"Importantly, the offer, in addition to the reward also includes a recommendation for indemnity from prosecution for any accomplice who didn't actually commit the crime, who first comes forward with information," Superintendent Hutchinson said.
"We are of the view there are people out there who have information about this homicide.
"We are hoping the reward and more importantly the indemnity offer an incentive to come forward."
The last confirmed sighting of the 12-year-old was when she was dropped at Marsden State High School on October 30, 2015.
On November 5 her decomposing body was found 40 kilometres away, on the banks of the Pimpama River.
Police believe the 12-year-old had a pre-arranged meeting with an unknown person the day she was dropped at school.
A team of investigators were working around the clock on her death in the wake of her body being found, however, in the past three months there has been no significant breakthrough.
Tiahleigh's pink backpack and school uniform, both crucial pieces of evidence in the case, have not yet been found.
Superintendent Hutchinson said detectives believed they knew where and when Tiahleigh was killed but would not yet divulge that publicly.
He said they were confident there was more than one person involved in the young girl's death.
"We certainly believe there is more than one person who knows what happened," he said.
"The indemnity is in addition to the reward and will be recommended for any person who didn't commit the crime. But it has to be the first person who comes forward, not the second. It's not available to the second person."
Anyone with information is asked to contact CrimeStoppers on 1800 333 000 or at crimestoppers.com.au