Samantha Murphy's disappearance is being treated as suspicious: a surprising twist in the investigation – as Missing Persons Squad detectives visit the family's home

The disappearance of Mother-of-three Samantha Murphy has been officially declared 'suspicious' by Victoria Police.

Victoria Police Chief Constable Shane Patton told Radio 3AW on Wednesday that the investigation had reached a new stage.

“It is certainly unusual that we have not been able to find any trace of hair or other evidence within that period,” he said at a news conference.

'It's suspicious. Whether that means there is foul play, I don't know, but detectives are clearly investigating a case where a woman has been missing for quite some time.”

His comments came as detectives from Victoria Police Missing Persons Unit visited the Murphy estate Wednesday morning.

The detectives, who arrived in a red ute, spent more than an hour inside before leaving.

The East Ballarat property is at the center of the investigation. It is where Ms Murphy was last seen on February 4, when she started her morning jog.

Ms Murphy's husband Mick Murphy, who is still supported by family members, is said to be working with the specialist unit, which is attached to Victoria Police's homicide unit.

Daily Mail Australia is not suggesting Murphy had anything to do with his wife's disappearance.

Last week, Detective Acting Chief Inspector Mark Hatt made no attempt to clarify how the investigation into his wife's disappearance would proceed in the future.

The veteran police officer told reporters on Friday that detectives would now investigate Ms Murphy's movements and interactions with others in the days before she disappeared.

'Absolutely, that will be a big part of our investigation. “We are digging into the background, investigating Samantha's movements in the days leading up to her disappearance as well as the people who knew her,” he said.

Part of the investigation – now called Operation Primus – will see detectives search Ms Murphy's computers and devices in the hope of finding clues.

The physical search for Ms Murphy has all but ceased by police, who are now only expected to re-enter the rugged woodland thanks to specific intelligence.

On Wednesday, community members continued the search for Ms Murphy in the hope she is found alive.

Ms Murphy, 51, left her home on Eureka Street in East Ballarat, northwest of Melbourne, to go for a run in Woowookarung Regional Park just after 7am on February 4 and has not been seen since.

Although police have released a CCTV image of Ms Murphy, captured outside her home on the morning she disappeared, they have failed to publicly reveal another image of her from neighboring CCTV cameras.

A grainy video feed from police last week claimed she was running in the opposite direction of where they were looking at the time and later revealed it was another jogger.

Chief Inspector Hatt said cameras at Murphy's home captured her walking into the driveway.

But he could not tell which way Ms Murphy went after leaving the property, despite the video feed capturing her doing so.

“It caught her leaving the address,” he said.

It remains unknown who was home at the time Ms Murphy fled.

It is known that she was expected back before 1 a.m. for a planned brunch appointment.

Ms Murphy's childhood friend Virginia O'Loughlan told Daily Mail Australia last week she did not believe her friend would have ventured into the rugged area where her phone was last 'pinged'.

'There's no way she could have fled that far. Absolutely not. “I am very confident,” she said.

On Thursday, state emergency services volunteers and police went into the bush in an area between the Canadian Plantation and Yankee Flat Road – about 15km from Ms Murphy's home.

“I think she went to brunch that morning, so I think she would be home by 9 or 10,” she said.

The commissioner's call for an investigation will be another devastating blow to Ms Murphy's three children.

Just hours earlier, Daily Mail Australia revealed that their mother's beloved dog, Ruby, had also died in the days following her disappearance after being hit by a car.

Last week, Jessica Murphy urged the public to continue searching for her mother.

“Mom, we love you so much and we miss you and we need you home with us. Please come home soon, I can't wait to see you,” she told reporters.

“Mom is a very strong woman, and she is far too determined to give up this fight.”

Anyone with information on Ms Murphy's whereabouts can contact Crime Stoppers on 1800 333 000.