Two Melbourne siblings say they were “jumping for joy” when their missing father Mark Tromp was found in Wangaratta, in northern Victoria on Saturday, but the circumstances behind his disappearance are no clearer.

Victoria Police are investigating the incident and Ella and Mitchell Tromp told media at their home at Silvan, east of Melbourne, that they could not disclose any more information about the case.

They spoke to their father last night after he was taken to the Wangaratta police station.

The pair, referring to the situation as a “family matter”, said they were unable to say what had sparked the case because police are still investigating.

“More than anything we’re just happy that dad is alive and he’s going to come back home — all of the family is going to come back home — and we can get back to normal,” Ella Tromp said.

“It was all very confusing. I still feel confused. Mum and dad’s minds weren’t in the best places.”

“It’s hard to explain,” Mitchell Tromp added.

Mr Tromp was found on the outskirts of Wangaratta after a “bizarre” trip that left other members of his family in hospital with stress-related complaints.

Police confirmed on Saturday evening that the 51-year-old had been found about 5.50pm after being spotted by a passerby.

The Border Mail reported he was found walking on the side of the road near Wangaratta Airport.

Police picked him up about 6.20pm walking towards the airport and took him to Wangaratta Police Station, where he was interviewed.

A police spokesman said he was in good health.

Authorities had been searching for Mr Tromp since Tuesday, after the Tromp family was reported missing and police found their Silvan home unlocked and abandoned.

Mr Tromp and his wife Jacoba drove off to NSW with their three adult children, Riana, Mitchell and Ella, on Monday, leaving credit cards and many of their mobile phones behind.

By Tuesday morning, Mitchell left the group near Bathurst and made his way to Melbourne via Sydney.

Then Riana and Ella left their parents at Jenolan caves and headed to Goulburn.

The moment Mark Tromp is taken into Wangaratta Police Station @bordermail @theage pic.twitter.com/0C0rBzKu99

— Ellen Ebsary (@EEbsary) September 3, 2016

There, the two daughters split up; Riana was found “catatonic” hiding in the back of a local man’s ute and Ella drove herself back to Melbourne.

Jacoba was found on Thursday in 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.

Police said the circumstances around the case were unusual and one officer described it as “the most bizarre case in 30 years”.

Mitchell Tromp said he and his siblings had to leave the trip because of their parents’ behaviour, which he said was out of character.

The route the Tromps took on their ill-fated family trip to NSW.

Timeline of the family road trip

Monday, August 29

• The family of five leave their Silvan redcurrant farm in a grey Peugeot station wagon with a large amount of cash, but bank cards and mobile phones are left behind
• Heading towards New South Wales, son Mitchell Tromp has his phone thrown out of the car window at Warburton, east of Melbourne

Tuesday, August 30

• Mitchell leaves the family trip at Bathurst
• The rest of the family travel to Jenolan Caves in the NSW central tablelands before the two daughters leave their parents at Goulburn
• Daughter Riana is hospitalised with stress-related health issues at Goulburn
• Police visit the Tromp family home after Mark and Jacoba are reported missing and find the house unlocked and paperwork everywhere

Wednesday, August 31

• The family’s car is found in Wangaratta in Victoria’s north-east after police receive a report that it was seen following another car
• Police pull the car over and a man, believed to be Mark Tromp, runs away into a nearby park
• The area is searched with sniffer dogs, but he is not found
• Mitchell and Ella Tromp make their way back to Victoria and arrive to find police at their farm

Thursday, September 1

• Jacoba Tromp is found and taken by a member of the public to Yass hospital where she is assessed for stress-related health concerns
• Mitchell and Ella appeal to the public for help to find their father
• Mitchell said his parents had mounting business pressures and were scared and paranoid when he left them on the trip

Friday, September 2

• Jacoba is transferred to Goulburn hospital to be treated alongside Riana.

Saturday, September 3

• Mark is found in Wangaratta after a passerby spotted him. Police say the 51-year-old is “safe and well”.