The search for an abducted grandfather has been expanded to thick bushland as his case continues to confound police.

Hopes are fading that investigators will find 85-year-old Chris Baghsarian alive more than a week after he was taken captive from his north-west Sydney home.

Baghsarian was reported kidnapped from the North Ryde property early on February 13 when three men stormed his home and bundled him into an SUV.

Investigators on Monday focused their efforts on Glenorie, a semi-rural suburb on the fringes of far north-west Sydney, near a national park and remote properties.

A vehicle linked to the case was seen in the area on the night of Valentine’s Day, more than 40 hours after Baghsarian’s disappearance.

The lead police investigator said CCTV footage and information from the public led them to Glenorie. But he declined to provide further details.

Police on Sunday appealed for information on two suspicious vehicle fires linked to the case late on February 16 in Westmead, 15 kilometres from the kidnap scene.

“Forensic links” were left behind in one burnt-out car that had been traced to Baghsarian and another relevant property in Dural, investigators said.

“This whole case has not been our normal kind of investigation in relation to kidnapping and a hostage,” Detective Chief Inspector Andrew Marks said on Monday.

Police believe the burnt-out vehicle was a 2022 Toyota Corolla with the Victorian registration 1UZ2BU. It was reported stolen from a Victorian address in January.

The stolen car also had fake Victorian number plates of DVT077, Marks said.

Those behind the arson failed to completely burn the car in their bid to destroy evidence.

Some of the remnants were linked to a derelict property in the semi-rural suburb of Dural, not far from Glenorie.

Police searched the vacant home on Thursday and Friday after identifying it as a makeshift stronghold for the kidnappers.

The mysterious case has stumped police who, in the absence of a ransom demand, have used media to directly appeal to the kidnappers to return the grandfather to a safe location.

“He (Baghsarian) has been taken over 10 days ago and every day … the concerns grow,” Marks said.

“Every day, it’s not a great feeling that we have in relation to his health and his survival.”

He again urged underworld operators to call police anonymously with any information on the kidnapping.

Asked whether Baghsarian was still alive, Marks said it was hard to speculate on his condition.

Baghsarian’s family spoke publicly for the first time last week, describing the kidnapping as a nightmare.

“Our family is living through a nightmare we never thought possible,” they said in a brief statement.

-AAP