Police are keeping tight-lipped about their investigation into Ariki Rigby's tragic homicide, almost a month after a car with the teen's body inside was set alight in Havelock North.

Detective Inspector Dave De Lange said on Friday police investigators were making "good progress".

They were still working through a large amount of information and piecing together the events leading up to Ariki's death, he said.

"We continue to encourage anyone with information to come forward and thank those that have already."

De Lange said he was unable to comment on specific details of the investigation, including how many police staff were working on it, for operational reasons.

"Our focus remains on holding the person or persons responsible for Ariki's death to account," he said.

"We have a number of detectives and police staff working on this investigation which we can increase or decrease as required."

On September 5 police launched an "unexplained death" investigation when human remains were found in a burned out car in a rural carpark near Havelock North.

Days later it was upgraded to a homicide investigation, and two and a half weeks ago police revealed that the body was that of missing 18-year-old Ariki Rigby.

Ariki Rigby's body was found by a member of the public in a burned out car in Hawke's Bay. Photo / Supplied

Family members and friends had been searching for her since they last had contact with her in late August.

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Her last contact with her sister was via a text message on August 23, with Anahera Rigby sharing it on social media on September 8 and urging anyone with information on Ariki's whereabouts to contact her.

Tragically, she was already dead.

The post was made six days after Ariki's body had been dumped in a vehicle that was then torched in the carpark at River Road Recreational Reserve.

Police believe the car was driven there between 10pm on September 2 and 7am on September 3.

It wasn't for a further two days that police realised that a body inside the car was human; initially believing the remains were of an animal.

Paula Connolly, National Homicide Service Manager for charity Victim Support NZ, said she could not speak about Ariki's case specifically, but in general the whānau of homicide victims would experience a range of emotions, including intense shock, grief and trauma in the weeks and months after.

Police speaking to the public at River Rd carpark in Havelock North, a week after Ariki Rigby's body was found in a burned-out car by a member of the public. Photo / Neil Reid

"People respond in different ways and while there are grief cycles everyone can refer to, it's not always like one, two, three going in a cycle, it depends on what is happening, it depends on the support that people have got and where they can tap into," Connolly said.

"Some people might want to go through that journey on their own and some people find it valuable to have support people. Some people find support within their whānau, some people find it externally with other agencies."

She said the investigation stage could be difficult for families, because they were still waiting for answers, and it could make it difficult for them to move on with their lives.

Connolly said an eventual court hearing was sometimes the first time family members in homicide cases had encountered the justice system, and it could be daunting.

"Further down the track there could be restorative justice and there could be, unfortunately, retrials and also parole hearings."

Connolly said a court process could take three to five years or even longer to get through, but what the whānau of a homicide victim went through could stay with them forever.

"You can get to the end of a trial, you can get to the end of a sentencing, you still have to live with the loss of a loved one."

- James Pocock, HBT