Police are searching a property in Sydney's west as part of their investigations into the disappearance of a 12-year-old schoolgirl, who went missing 18 years ago.

Key points: Quanne Diec disappeared after leaving her Granville home for school in 1998

Quanne Diec disappeared after leaving her Granville home for school in 1998 A 49-year-old man went to police yesterday and has been charged with murder

A 49-year-old man went to police yesterday and has been charged with murder Police looking for her remains at a property in western Sydney

Officers said old-fashioned detective work led to a man being charged yesterday with the murder of Quanne Diec.

Vinzent Tarantino, 49, did not apply for bail and it was formally refused when he appeared in Sydney's Central Local Court charged with murder, detaining a person for advantage and possessing a knife.

Tarantino, who is also known as Victor Gerada, lived several hundred metres from the Diec family home at the time and police will allege he knew the missing girl's movements and deliberately targeted her.

Against the advice of his solicitor, Tarantino made a statement to the court alleging his brother and partner had been murdered in retaliation for what he had done.

"I believe my brother … and my partner … have been murdered in retaliation for what I've done," he told the court.

However, he did not detail how, or when, that occurred.

Vinzent Tarantino did not apply for bail at Sydney's Central Local Court. ( ABC News: Vincent de Gouw )

Quanne is believed to have been abducted on her way to school from her Granville home in 1998.

Court documents allege Tarantino enticed Quanne into his car on nearby Factory Road with the intention of holding her for ransom and "caused her a substantial injury".

A search of a residence for Quanne's remains is underway today.

No details on how Quanne died

At a media conference in Sydney, Superintendent Scott Whyte from Rosehill Local Area Command said the man charged was not known to the 12-year-old.

He said he hoped police would get assistance from the accused in being able to recover Quanne's remains.

"That's something that we hoped would play out for sure, but again as I said our priority is to get Quanne home for her mum and dad," he said.

Superintendent Whyte declined to give many details about exactly what had happened to Quanne almost two decades ago, although he did say police believed she was alive for only a short time after she was abducted.

"We do have an idea of how it's played out but obviously because of matters before the court, I certainly won't be going into any specifics of that today," he said.

In 1999, the NSW Government increased the reward being offered for information leading to the location of Quanne, from $100,000 to $200,000.

Superintendent Whyte was asked by reporters if the reward was being claimed.

"I think it's important to reiterate that the 49-year-old man was the suspect in this matter. He attended the police station as a result of the investigation that these outstanding investigators were conducting," he said.

"No, he is not trying to claim this reward.

"We are still certain there are people out there who can assist us with this investigation so we have asked them to come forward and assist us."

The Granville property where police are searching for the remains of missing girl Quanne Diec. (ABC News)

Superintendent Whyte appealed to the media to allow the missing girl's parents privacy in the wake of the development.

He also said the man was known to police and that they had never given up on finding Quanne.

"This investigation has been going since 1998. The investigators have interviewed and re-interviewed," Superintendent Whyte said.

"The NSW Police just never give up hope and their outstanding work has led directly to this man being charged last night."

He said police had not ruled out further arrests.