The terrain in the Victorian Alps has been challenging for investigators.(Nine)
Detectives have established Mr Hill was camping alone with his Landcruiser in the area of King Billy and Bluff Track, between March 11 and 13.
An older person or pair was later sighted at the Black Snake Creek, Eaglevale River crossing and the Ollies Jump area between March 22 and 23, however, police have never been able to determine if it was the missing campers.
Anyone who was in the area of Howitt Plains and Zeka Spur Track on March 19 or 20, the Wonnangatta Valley and Wonnangatta Station between March 20 and 24 who has not yet made contact with police, are urged to come forward.
Police scour bushland in search for missing Victorian campers
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Missing Victorian campers: a year on, search returns to initial site
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New clue uncovered in search for missing Victorian campers 15/04/2021|1min
Victorian detectives have uncovered a new clue in the renewed search for missing campers Russell Hill and Carol Clay.
Two shovels were discovered in a new search area near Mount Hotham.
The secret lovers were not heard from since they went camping in the remote Wonnangatta Valley in March last year.
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Police have found a new clue in their renewed search for a couple who vanished on a camping trip more than a year ago while they were having a secret affair as they declared somebody else is involved in the pair s baffling disappearance.
Detectives uncovered two shovels as they were trawling through dense bushland at an incredibly remote location at Mount Hotham in the Victorian Alps about midday on Wednesday while desperately looking for signs of Russell Hill and Carol Clay.
The shovels were placed into plastic bags and carried from the scene by officers so they could be forensically examined.