In the immediate aftermath, police described Mr Saunders' death as “a tragic accident”.

Last year, Acting Inspector Paul Algie said it was just a tragic accident with no suggestion of foul play.

However, in the days after the death detectives received information that Mr Saunders' death was no accident and forensically-examined evidence has since supported that theory.

"Information we received during the course of our coronial investigations has led us to believe that the death is suspicious and we have a number of detectives and police experts investigating this incident," Inspector Pettiford said in a statement on Friday.

Police searched the property again on Sunday with the help of SES personnel and found "several items of interest".

They also reinterviewed Mr Saunders' two friends who discovered the body and have established other persons of interest who they hope to talk to soon. 

Inspector Pettiford said the tip-off came from people who were either known to the victim or the persons of interest and that detectives expected to lay charges in the future.

He added officers were looking into a potential motive for the murder, but ruled out any relation to gang violence.

Police do not believe there was a delay between Mr Saunders going into the woodchipper and the triple-zero call being made, with Inspector Pettiford saying emergency services were notified "virtually straight away".

Homicide detectives are now working with officers from the Gympie Criminal Investigation Branch on the case.

Anyone with information is urged to contact Gympie detectives, Policelink on 131 444, or Crime Stoppers on 1800 333 000.

Mr Saunders and two friends were using a hired woodchipper at the rural property on November 12 when it was believed the victim fell into the machine and died “within a few seconds”.

The trio had spent the past three weekends at the property "doing a favour" for the resident, who was a family friend.

Police said the resident was home at the time of the incident but didn't see anything.

Detectives also said the man's friends didn't see him enter the woodchipper, but they did find him inside the machine and tried to pull him out.

In the aftermath, the Forensic Crash Unit and Workplace Health and Safety Queensland attended the scene, while the Disaster Victim Identification squad was used to confirm the victim's identity.

- with AAP