Relatives of two hikers missing in Victoria's alpine region have made an emotional plea for their return as rescue efforts ramp up before temperatures drop.
The couple have spent three nights in frosty conditions, with the temperature dropping to five degrees on Monday morning.
Officers on horseback and foot plus a police helicopter are looking for experienced hikers Trevor Salvado, 60, and Jacinta Bohan, 58 who disappeared at Mount Buffalo on Friday.
The search effort doubled in size on Monday, with more than 100 search and rescue personnel working their way through the rugged terrain.
Inspector Joy Arbuthnot said the Essendon couple were due to meet friends for an annual long weekend getaway and were last seen at a caravan park in Bright in their Skoda car on Friday.
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They were due back from a bushwalk at Reservoir Track, on Mount Buffalo, around midday but did not return. Their car has since been found.
Difficult terrain was making it hard for crews to make their way through the search area and air crews were searching day and night, Insp Arbuthnot said.
"(The couple have) been coming to this area for a long time, they are familiar with the conditions here and know the area quite well," she said.
"We are still treating it as a missing person case."
The couple's son Nathan said he last spoke to his parents on Wednesday or Thursday and they told him they'd be gone for a few days.
"Come home please. I miss you," he told reporters on the sidelines of the search on Monday.
"We're looking for you. We're trying the best we can."
Ms Bohan's sister, Maria Bohan, said the pair's large extended family had come together to support each other during a difficult time.
"We've been getting loads of messages and good old-fashioned prayers," Ms Bohan said.
"We've got a big team behind us, and we can't speak more highly of the police."
Speaking earlier, police Sergeant Martin Torpey shared a theory about what might have happened to the hikers.
"It's quite treacherous and there are some ravines with a steep drop," he told the Herald Sun.
"We think one may have fell and the other has gone down to help them. It's rare that two would go missing."
Mr Salvado has short grey hair, blue eyes, a grey moustache, a fair complexion, and is about 183cm tall with a medium build.
Ms Bohan is about 170 cm tall, thin, and has light brown/blonde short hair, blue eyes and a fair complexion.
