Russell Hill and Carol Clay were last heard from on March 20 last year while camping in the Wonnangatta Valley.

Investigators have eliminated multiple vehicles from their investigation, and believe a blue mid to late 1990s Nissan Patrol with a trailer may be linked to their disappearance.

Detective Inspector Andrew Stamper said the vehicle may have headed to Mt Hotham after the incident, which is being treated as suspicious.

"Throughout our extensive and significant investigation over the last 20 months, we have not been able to eliminate this blue four-wheel drive from our inquiries," he said.

"We have witness statements that put this blue vehicle and its trailer in the valley at the time Russell and Carol were there, and indeed near the spot that they had set up their camp.

"Detectives have also been given information that a vehicle attempted to leave the valley late at night on the evening of Friday 20 March, but the Myrtleford gate was closed because of the bushfires, meaning that the driver had to make a complicated turn back in the direction from which they had come.

"That same vehicle is also spotted on two cameras at the top of Mount Hotham, consistent with where a vehicle would exit the valley given the closure of the Myrtleford gate.

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"We understand that initially, given the confusion around COVID-19 and state-wide lockdowns that people may have been reluctant to come forward, or that someone may simply have missed our repeated appeals for information.

"But if you are the driver of this blue Nissan Patrol, or you know who is, we would urge you to come forward - if nothing else, so we can eliminate you from our inquiries and move forward.

"Both families are still desperate for answers about what happened to Russell and Carol and why, and I know our investigators are doing all they can to try and get those answers for them.

"If you do know something or have heard something, no matter what it is, then I urge you to come forward and hopefully we can continue to fill in all the pieces of this puzzle until we get the result and answers both families deserve."

A drone located in the Gippsland area earlier year and handed into police was examined and investigators have confirmed it was not Mr Hill's.

Two shovels located at Mount Hotham in April have also been forensically tested but so far police have not been able to link them to the campers' disappearance.

Anyone with information can call 1800 333 000.

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