Police have put out a warning to the person responsible for the disappearance of two Victorians in the rugged high country 19 months ago.

It’s yet to be determined what happened to Russell Hill, 74, and Carol Clay, 73, but investigators have long believed it is likely a third party was involved in their disappearance.

“They should be very uncomfortable,” Detective Acting Sergeant Brett Florence of the Missing Persons Squad told the Herald Sun.

“We will leave no stone unturned until we do (get a result).”

Squad detectives on Tuesday joined with the families of the pair to renew an appeal for anyone with information on their whereabouts to come forward.

Mr Hill and Ms Clay were last heard from on 20 March, 2020, while camping in the Wonnangatta valley.

Mr Hill left his Drouin home on March 19 and picked up Ms Clay from her home in Pakenham in his white Toyota Landcruiser.

He was last heard from on March 20 when he made a call via HF radio saying he was at Wonnangatta Valley in the Victorian Alps.

Ms Clay told friends she was heading away and expected to return home on March 28 or 29.

Investigators have been told they were camping together at Wonnangatta River near the Wonnangatta camping ground.

Campers found Mr Hill’s car with signs of minor fire damage at their campsite, which was completely destroyed by fire, near Dry River Creek Track on March 21.

Victoria Police want to speak to anyone who was in the Wonnangatta area around that time, including campers, 4×4 day trippers, hunters, fishermen or trail bike riders, regardless of whether they saw or heard anything.

“This is so police can continue to eliminate people and vehicles from their extensive investigation,” they said in a statement on Tuesday.

They also want to speak to anyone who was in the area of Howitt Plains and Zeka Spur Track on March 19 and 20, and the Wonnangatta Valley and Wonnangatta Station between March 20-24.

“Investigators have had the opportunity to speak with both the Hill and Clay families in the past week and to say their grief is still very raw would be an understatement,” Detective Inspector Andrew Stamper said.

“Both families are also 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.”

Multiple searches have been conducted in and around the Wonnangatta Valley during the past 19 months, including with cadaver dogs.

-with AAP