A New Zealand father has rushed to Western Australia where his son is missing in mysterious circumstances.

A massive search has been launched for Michael Junior Huria, 23, who was last seen in Ellenbrook, Perth on Monday when he left his home about 4.15am.

He failed to return home and was reported missing. Police are investigating whether his disappearance is linked to reports of a car hitting a pedestrian in the area, according to the Herald Sun.

His father, Mark Huria, has flown to Australia from Wellington to assist.

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Huria's stepmother, Lynell Huria, said the family was extremely worried.

"We don't really know the current status apart from what the police have said to everyone through the releases in Perth.

"The family is really worried, really worried about him and hoping he turns up soon."

She said they had "no idea at all" where Here may have gone.

"We have been just really focused on trying to find him and keeping our phones to any calls."

The wide scale search has involved a social media campaign, search and rescue crews, police horses and a helicopter.

The Herald Sun

reported that Huria's vehicle, a white Mitsubishi Triton, was located on Wednesday but Huria has not been heard from.

His disappearance is out of character and police have concerns for his welfare.

Huria's father and his brother, Tamati, addressed media on Saturday.

According to Perth Now, his brother said Huria had been in a "slow decline over the last couple of weeks" and was most likely in a "disassociated state of mind".

His brother Tamati Huria said Michael had been in a "slow decline over the last couple of weeks" and was most likely in a "disassociated state of mind".

He added because of this, Michael was "a bit inclined" to go on a spiritual journey.

"But it is very unusual. Usually in the past he comes forward if he needs help or if he's not ashamed or shy to ask for help," he said.

Mark said it wasn't unusual for his son to be awake that early as up until recently he had worked in the building industry.

"His white ute had run out of petrol - we know that because I tapped on the petrol tank and it hadn't been siphoned ... so we think he's run out of gas and tried to get gas and maybe it was dark and he got lost," Mark Huria said.

"Enquiries into his whereabouts continued overnight and the search has escalated this morning with police horses, State Emergency Service volunteers and a police helicopter being called in to assist with the search," police said in a statement.

The RAC rescue helicopter is also helping with the search.

Huria, who is believed to have links with Wellington and Hawke's Bay, also uses the surname Sullivan.

It is believed he was wearing a white shirt, blue shorts (possibly denim) and was not wearing shoes.

Police said that as part of their investigation they were reviewing a report received on Monday night about an incident in which a woman believed her car may have hit a pedestrian near Great Northern Highway and Apple Street in Upper Swan, the Herald Sun reported.

"The driver ... believed her car and the pedestrian made contact. Despite enquiries at the time the pedestrian was not located," said Acting Inspector Phil Bonner.

He said it was out of character for Huria to go missing.

Bonner urged anyone who may have picked up any hitchhikers in the area to call police.

The woman who believed she may have struck a pedestrian on Monday night was assisting police.

"She's obviously distressed about the whole incident," he said.

"She's done the right thing, she's stopped and contacted police and we are conducting enquiries with her."

On social media, Huria's family were also expressing their concerns.

Many shared photos of Huria and were offering their support and condolences to each other.

His brother, Tamati Huria, shared a news report of the disappearance.

"Anyone in the bullsbrook are having any information would be much appreciated!!!! [sic]," was his caption.

He said the family were "keeping our mana strong" as they waited for news.

"Thank you everyone for you support goes along way everything in our power is being done to bring him back to his whanau!! Thanks again."

Margaret Sullivan, their grandmother, wrote: "Darlings this is a difficult time for all of you stay strong united and trust the Lord is caring for Michael in his hour of need karaka is important and wrap yourself in love and never give up [sic]."

Paula Sullivan said: "Where are you my beautiful nephew? Please. We love you XX."