Search continues as police 'very doubtful' they will find Samantha alive

Almost three weeks since Ms Murphy was last seen, police researched areas in Mount Clear on Friday February 23.

Along with the ground search, police are looking at 12,000 hours of CCTV and 500 pieces of information related to the investigation.

Detective Acting Superintendent Mark Hatt said they are investigating if other people were involved in Ms Murphy's disappearance.

He could not comment if he thought these people were known to Ms Murphy.

He said everyone in relation to Ms Murphy is a person of interest, including family, friends and work colleagues.

"We are speaking to everyone that was in her life."

They are urging anyone who may have seen vehicles or people acting suspicious in the area on February 4 to come forward and contact Crime Stoppers.

Acting Superintendent Hatt said they have ruled out Ms Murphy suffering any sort of medical episode.

"We have no information to suggest that she left the area of their own accord," he said.

He said they were very confident they had tracked all of the movements to and from the Murphy's home on the Sunday morning.

Police have looked at some vehicles but have not seized any.

The Mount Clear area was searched extensively during the first week of Ms Murphy's disappearance.

Acting Superintendent Hatt said they were searching in the area again because of information from Ms Murphy's phone.

During the first week of the search police and SES volunteers were looking for Ms Murphy, her phone and watch.

"What we're looking for today is more intricate details of what may have happened [on February 4]," Acting Superintendent Hatt said.

Acting Superintendent Hatt said this could be smaller items, her phone or a body.

"That area has been searched for Samantha herself and we have not found her in that area," he said.

"Unfortunately, given the time and the fact we've found no trace of her, we do have severe concerns and I'm very doubtful that she's still alive."

He said there were between 20 and 30 working on the Mount Clear ground search.

Police anticipated they would finish the search on Friday but if they found new information they would continue.

Acting Superintendent Hatt reconfirmed on Friday that police knew Ms Murphy left her home on foot on Sunday February 4 because of CCTV footage from her home.

They don't have any more CCTV footage of Ms Murphy but said they believed she entered the Canadian State Forest [Woowookarung Regional Park] for her run.

Within an hour of leaving home, police believe she made her way to the Mount Clear area.

Acting Superintendent Hatt said they knew Ms Murphy would often go for runs of different distances.

He said on Sunday they believed she intended to go for a seven kilometre run.

Acting Superintendent Hatt said the search for Ms Murphy was the number one priority for Victoria Police.

"We will do whatever we possibly can to find Samantha, if it takes months, years, we will do that.," he said.

"The Ballarat community has been absolutely fantastic both in their search efforts, their support for our investigation and their cooperation with our investigation."

He said there is no evidence anyone else in the community is at risk.

Community members have organised their own search for Saturday February 24.

Acting Superintendent Hatt said he urged people involved to contact police immediately if they find anything.

In a press release, Samantha is described as Caucasian, about 173cm tall with a slim build and shoulder-length blonde hair.

She was last seen wearing black half-length leggings and a maroon/brown coloured singlet.

Anyone who sights Samantha is urged to contact triple zero (000) immediately.

Anyone with any other information about Samantha's current whereabouts is urged to contact Crime Stoppers on 1800 333 000 or make a report online at www.crimestoppers.com.au