How the bizarre mystery unfolded.

An internal document circulated among NSW police warned the family of five may be suffering from group delusional schizophrenia after they hurriedly fled their Victorian home on Tuesday, amid apparently unfounded fears for their lives.

There has also been speculation they may be suffering from a rare psychiatric condition known as folie à deux, a French term meaning “madness of two” which almost always occurs in close-knit families, between husband and wife and between siblings.

But Mitchell Tromp denied the family had been diagnosed with any shared mental health complaint, as the search for his missing father Mark entered its fifth day.

The last official sighting of the father-of-three was on Wednesday, when he fled into parkland in the northeastern Victorian town of Wangaratta, after tailgating a young couple who had been out playing Pokemon Go.

Police are investigating a number of unconfirmed sightings in New South Wales and have so far discounted one in the rural town of Bega.

Forensic evidence has been taken from a room at the Millers Cottage Motel in Wangaratta, after its owners found a room door ajar about 9.30am on Friday.

The bathroom appeared to have been used, the bed may have been slept in and a muesli bar wrapper was found on the floor.

But the hunt continues.

Mark Tromp remains missing, while his wife Jacoba remains in a fragile mental state in hospital.Source:Facebook

Mr Tromp, his wife Jacoba and their three adult children hurriedly fled their home in Silvan, in Victoria’s picturesque Yarra Ranges, without any clear destination on Tuesday, sparking a baffling mystery.

Police found their farmhouse unlocked and abandoned, with passports, credit cards and mobile phones left behind and keys still in car ignitions.

Mitchell Tromp told media on Thursday his parents feared for their lives but police on Friday said the couple had not been threatened or followed, nor were they under financial pressure.

“I’ve never seen anything like it,” Mitchell Tromp said.

“It’s really hard to explain or put a word on it but they were just fearing for their lives and then they decided to flee.”

He said his father “thinks people are after him. He’s not in a good state of mind”.

Sergeant Mark Knight said there was absolutely no evidence anyone was after the family.

“We can categorically say there was no one following any of them,” Sgt Knight told the Herald-Sun.

“There has been no physical threat to this family at all. It was in their minds.”

Mitchell and Ella Tromp speak to the media after their parents’ disappearance. Picture: Andrew HenshawSource:News Corp Australia

Mitchell Tromp told Fairfax Media on Friday reports his family was suffering a shared mental condition were simply not true, after the revelations of the internal NSW police document that speculated the family could be suffering from group delusional schizophrenia.

The family fled their home in daughter Ella’s silver Peugeot SUV.

Mitchell, 25, was the first to abandon the bizarre road trip, fleeing the family near Bathurst to return to Melbourne via Sydney.

Riana, 29, and Ella, 22, left their parents at the Jenolan Caves in the Blue Mountains, before heading to Goulburn.

The Tromp family home in rural Silvan. Picture: Andrew HenshawSource:News Corp Australia

Riana was found in a “catatonic” state in the back of a local man’s ute in Goulburn on Friday, while Ella drove herself back to Melbourne.

Their mother Jacoba was found on Thursday in a Yass hospital and has since been transferred to Goulburn hospital where Riana is also being treated.

Police say both women are in a fragile mental state.

Riana Tromp was found in a catatonic state, hiding in the back of a local man’s ute in Goulburn.Source:Facebook

Mitchell Tromp said “everyday pressures” had got to his parents and they wanted to flee.

They left their mobile phones at home out of fear they would be followed and Mitchell Tromp said he was forced to throw his own phone from the car window while on the road for the same reason.

How the bizarre mystery unfolded.Source:The Daily Telegraph

WHAT WE KNOW

• Mark and Jacoba Tromp and their three adult children Mitchell, Ella and Riana leave their Silvan home on Monday, August 29

• The family left in Ella’s grey Peugeot and headed to NSW

• On Tuesday morning, Mitchell leaves the group near Bathurst and makes his way to Sydney and then catches a train to Melbourne

• Ella, Riana and parents make it to Jenolan Caves, about 150km west of Sydney

• At the caves, on Tuesday, the daughters leave their parents and make their way to Goulburn

• Ella and Riana split up at a Goulburn service station because they want to get home different ways

• Riana found under mental stress on the side of a road near Goulburn and stopped by police in her attempts to go home.

• Riana taken to hospital, where she remains

• NSW Police informs Victoria Police about the family

• Ella acquires a car, drives home and arrives at the family’s Silvan farm on Tuesday night while Victoria Police are there

• Mitchell arrives in Melbourne on Wednesday morning. At one point on the trip Mitchell admitted to having his mobile phone, but he voluntarily threw it out the window at Warburton.

• Ella’s Peugeot found in Victoria, in Wangaratta, on Wednesday night

• A man, believed to be Mark, seen running from the car.

• On Thursday, Jacoba Tromp is taken to Yass hospital by a passer-by who sees her in the NSW town

• Extensive searches of Wangaratta fail to find Mark Tromp

WHAT WE DON’T KNOW

• Where Mark Tromp is

• How Mark and his wife became separated

• What the parents’ movements were after daughters left them

• Why the family was “emotionally traumatised”

Support and information about mental health issues can contact Lifeline on 13 11 14 or beyondblue on 1300 224 636.

— With AAP

kim.stephens@news.com.au