They also started further forensic examination on Tuesday at a Walgett house and seized several items for tests, police said.

Roxlyn Bowie, aged 31 at the time, was reported missing after she was last seen at her home in the town about 6pm on Saturday 5 June 1982.

She left behind her husband and two children, who were aged six and almost two at the time.

Local police started an investigation into her disappearance before the case was assigned to the Homicide Squad.

A coronial inquest in September 2014 held at Dubbo found Mrs Bowie had died but the cause of death was undetermined.

Her body has not been located.

The State Crime Command's Robbery and Serious Crime Squad has led a renewed investigation into her disappearance and suspected murder under Strike Force Maluka.

As part of ongoing inquiries, detectives and specialist forensic investigators started a thorough forensic examination, including luminol testing, at a home in Walgett on Tuesday.

So far during these examinations, several items which may be relevant to the investigation have been located and seized to undergo further forensic testing.

As their investigation continues, strike force detectives have released images of a diamond ring that was similar to one sold from a Bankstown pawn shop on Wednesday 6 June 1984.

Robbery and Serious Crime Squad Commander, Detective Superintendent Danny Doherty, urged the person who purchased that ring to come forward.

"This ring is believed to have belonged to Roxlyn Bowie prior to her suspicious disappearance and, despite numerous searches, has never been located," Det Supt Doherty said.

"We want to stress that whoever purchased the ring is not in any legal trouble; we are seeking them as the information they may provide could be of great benefit to the investigation.

"As part of this renewed investigation, we have conducted further forensic testing at the Walgett home where Roxlyn was last seen alive.

"While we await the results of these examinations, we continue to call on the community to tell us what they know.

"It doesn't matter how long it takes to find answers, our detectives are committed and will leave no stone unturned as they pursue justice for Roxlyn and her loved ones."

Det Supt Doherty reminded the community that a $1 million NSW Government reward remains on offer for information leading to the location of the body of Roxlyn Bowie or for information leading to the arrest and conviction of the person or persons responsible for her murder.

Investigations under Strike Force Maluka are continuing.