CCTV of van released as police continue 'painstaking' investigation into $24m mansion fire

Police have released new CCTV today as they continue their "painstaking" investigation into a suspicious fire that destroyed a $24 million mansion on Sydney's Lower North Shore earlier this year.

Investigators believe the silver Toyota HiAce Van with roof racks caught in the footage could be the key to solving this case from earlier this year.

An unknown man was captured running towards the van a short time after the fire took hold, and police believe he left the scene in the Toyota.

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The fire engulfed the home at Cliff Road in Northwood at about 10.50pm on September 3.

A crime scene was established and examined by specialist forensic officers, who determined the fire was deliberately lit.

Fire and Rescue NSW said the home was "totally destroyed" and no one was at home and no one was home at the time.

9News understands the home's owner and businessman, Owen Chen, has been assisting police with their inquiries.

Chen lives next door to the damaged home.

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Detective Chief Inspector Richard Puffett said police had been undergoing a "painstaking" investigation.

"We believe the male depicted on foot in the vicinity of the fire is linked to that van," Puffett said.

"We believe there is possibly more than one person involved and we believe that may have been the passenger in that van."

Anyone with information, or dashcam footage of cars on Cliff Road on September 3, should contact NSW Crime Stoppers on 1800 333 000.