Police and emergency services have expanded their search for a 21-year-old man who has been missing since Thursday in "freezing cold" conditions in Victoria's high country.

Key points: Police say they have "grave concerns" for Poshik Sharma

Police say they have "grave concerns" for Poshik Sharma The 21-year-old was last seen leaving a Marysville pub on Thursday afternoon

The 21-year-old was last seen leaving a Marysville pub on Thursday afternoon It has been cold, rainy and even snowing in the area since he disappeared

Poshik Sharma was last seen leaving the Duck Inn in Marysville, north-east of Melbourne, at about 3:50pm on Thursday.

Mr Sharma, an Indian national who lives in Werribee, in Melbourne's outer west, had been travelling with friends to the state's alpine region.

They were staying the night a short walk from the Duck Inn and had a disagreement before he left the pub.

"We think he may have been going back to his accommodation," Inspector David Ryan said.

"So in the space of about 50 metres this man has disappeared. He's walked off into the bush … or he's got a lift from someone. That's what we're hoping."

State Emergency Service (SES), Search and Rescue and police personnel have expanded their search to the bush, walking tracks and waterways surrounding the small town.

It has been a rainy and cold week for Marysville and its surrounds, with temperatures dipping to freezing overnight.

Emergency services workers have come from Melbourne and other parts of the state to join the search. ( ABC News )

Inspector Ryan, who is overseeing police in the search for Mr Sharma, said it had snowed on Saturday and was "freezing cold".

"Our best hope is that Poshik has found some shelter. His condition, if he hasn't found some shelter, is likely to be very poor at this stage and that's why we hold really grave concerns for his safety," he said.

Dam drained as part of search

SES crews from other parts of Victoria have joined the search, alongside local officers, police dogs, and bush search and rescue experts.

Police began to drain a nearby dam on Sunday afternoon while search and rescue teams scoured the water.

"If he's tried to walk off, had a mishap and gone into the water — it's not a good outcome," Inspector Ryan said.

Julie Cowan, founder of Search and Rescue Dogs Australia, said her dogs had become "very interested" in the body of water.

The search was expanded on Sunday as fears grew for Mr Sharma's safety. ( ABC News )

Ms Cowan described the conditions as "treacherous".

"Most of the tracks are wet and slippery, most of the trees have fallen over … I can't see him wandering off into this thick dense bush, given his history."

Disappearance is out of character, police say

Inspector Ryan said the disagreement between the friends was "nothing that would suggest he would do anything other than return to the accommodation".

"His disappearance in these circumstances is out of character, there is nothing to suggest that he is in any way suffering any psychological issues," Inspector Ryan said.

The friends had been drinking alcohol, but police did not believe intoxication was a factor in his disappearance.

Mr Sharma's social media and online banking accounts have not been touched since Thursday, and police were not able to trace his mobile phone.

He was wearing a red scarf, "distinctive" red shoes, black beanie and black puffer jacket when he was last seen, and police are urging anyone who may have seen him to come forward with information.

Family members joined the call for help on Sunday morning, telling reporters Mr Sharma and his four friends had stopped at Marysville on their way to the Mount Buller ski resort.

"I don't know where he is now, so please help me to find him," his sister Samta Sharma told Channel Nine news.

Inspector Ryan said they had not heard from anyone who had sighted Mr Sharma, and police were "desperate" for information from the public.