New details have emerged over teenager Ariki Rigby's killing, with her heartbroken sister saying she believes she was beaten to death before being dumped in a car that was then torched.

And as police continue to hunt her killers, Anaherā Rigby has made an impassioned plea for those who know who did it to stop "protecting" them.

A month and a half has now passed since Ariki's body was found in a burnt-out car in a rural carpark in Hawke's Bay.

The 18-year-old was killed during an unplanned holiday in Hawke's Bay to see her father and stepmother.

Sister Anaherā believes her life was brutally ended on the day she was scheduled to return to Auckland.

In an exclusive interview with the Herald, Anaherā said she was adamant her sister had been "badly beaten" and was dead before the car was set alight.

"She would not have stayed in a car while it burned," she said of her sister, adding she was a very determined person.

"I said that to the police too. I told them she must have already been dead before they torched the car."

Ariki Rigby was working in a bar in Auckland prior to going on an unplanned holiday to Hawke's Bay. Photo / Supplied

The dog walker who discovered Ariki's body has previously told the Herald she had multiple bone breaks and fractures.

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Police say they are making "good progress" and working through the information provided to them.

They would not engage on what injuries the teenager had suffered before her body was badly burned in the car fire.

But Anaherā believes her sister would have fought for her life.

She was disgusted at the actions of Ariki's killers.

"To me that is cruel," Anaherā said.

The "Legacy" women empowerment T-shirt Anaherā Rigby, pictured along with cousin Michael Ngahuka, is wearing was placed in homicide victim Ariki Rigby's coffin before she was buried. Photo / Supplied

"My baby sister didn't deserve to die like that. Even if she wasn't my sister, nobody deserves to die like that ... beaten up, shoved in the back of a car and then torched and then left there.

"They tried to cover it up and get rid of all of the evidence and now they're walking around free."

She also urged those who knew the truth to contact authorities, saying her sister's killers were "dangerous people" who needed to face justice.

When asked what her message was to those who know who did it, she replied: "Not to hide them any more. People know something, they do, and they are just too scared to say who they are, and what they have done.

Flowers, cards, balloons and other tributes placed by loved ones of Ariki Rigby at the spot a car containing her body was torched near Havelock North. Photo / Neil Reid

"Maybe they love these people and they don't want to turn them in. But they need to remember that those people are dangerous ... they took a little girl's life, she was only 18 years old ... she had a whole life in front of her.

"Our community isn't safe with them walking around, even if they are your family or your friends. They could do it again."

Ariki's body was found in a car that was driven to the River Rd Recreational Reserve, on the outskirts of Havelock North, between 10pm on September 2 and 7am on September 3, before being torched.

A popular dog-walking site, police were alerted on September 3 that a vehicle had been burnt out in the carpark.

But the first officers at the scene didn't realise the charred remains in the car were human – instead thinking they were an animal's.

It wasn't until a dog walker rang them again two days later – horrified to discover the body which remained in the car featured shoulder-length hair and was wearing a necklace – that police launched an "unexplained death" investigation.

Police searching for any potential evidence a day after officers realised burnt remains in a car were human. Photo / Neil Reid

That was upgraded to a homicide investigation several days later.

Ariki - born and raised in Hawke's Bay – had lived in Auckland for the past year.

She was killed during an unplanned holiday back to Napier.

"She was going to go and see our little brother in King Country, but he wasn't home, " Anaherā said. "So she changed her mind and went to Hawke's Bay instead."

She spent a month in the Hawke's Bay.

"That very day that they did this to her, she was supposed to come home," she said.

"She even put a status on Facebook that she was coming home and whoever wanted to come and visit her to see her before she left [for Auckland]."

Anaherā described her relationship with Ariki as "very close".

During the last text exchange between the pair in late August, Anaherā told her younger sister that she loved her and she hoped she was safe. Ariki replied that she was okay.

She said she wasn't concerned about a lack of contact over the next few days as she realised Ariki would be busy catching up with friends and family before returning to Auckland.

But just days before the grisly discovery at River Rd Recreational Reserve she feared Ariki was in trouble and made appeals around the Hawke's Bay for any sightings.

"I couldn't find her and that was a bit different for us because it is easy to find Ariki. I can always find my sister," she said.

Ariki Rigby's sister remembers her for being full of life and on a mission to be the best person she could be. Photo / Supplied

"My sister was mischievous ... so occasionally I would have to go find her and see if she was okay. And [I thought] this was another one of those times.

"Ariki ... would have still been alive when I started looking for her."

Her heart sank when she read on September 6 that police realised the remains in the torched car were human.

"I knew it was my sister," Anaherā said.

"I was dreaming of her ... she was telling me it was her. I actually wasn't surprised once they [police] told me it was her. I'm her sister, [if she was alive] I would have already found her and I hadn't ... I just knew."

While Ariki had been reported missing to the police by three of her cousins, Anaherā was heavily involved in helping with the formal identification of her remains.

That included giving police a full description of Ariki's jewellery – including some items she had gifted her that her younger sister was wearing.

"That is when I was scared ... when I described my sister's jewellery and they asked for more details on the specifics," she said. "When they did that, that is when I knew it was my sister.

"I broke ... I had my cries and then went home to organise my baby sister's tangi, to go and look after my family."

Dental records – which Anaherā located – were also used to confirm her identification, which was made a week after police launched their investigation.

She said police had told the family they were making "good progress" with the homicide investigation.

Family members were also being proactive in trying to uncover information that could lead to arrests, including putting up flyers around Hastings and Flaxmere.

The A4 sheets of paper feature two photos of Ariki, with the message: "Any information on Ariki Rigby's death would be much appreciated.

"Family want, and deserve closure. We won't rest until we do. We'll find out who did this to our girl. You didn't deserve this!"

Family of Ariki Rigby have placed flyers in shops around Hastings and Flaxmere appealing for information. Photo / Neil Reid

The flyers include Crime Stoppers' tip line where anonymous tips can be made.

Anaherā said any information the family received was reported straight to the police.

Police officers went back to Riverside Recreational Reserve a week after Ariki Rigby's body was dumped there in a bid to find any leads. Photo / Neil Reid

"We are very hopeful and confident that with whatever information they have they will find them [those responsible] soon," she said.

Ariki had lived in Auckland for the past year. Her sister said she worked behind the bar at a nightclub.

She was living in an apartment and had just bought herself a van before going on holiday.

The location where the car containing Ariki Rigby's body was torched is a popular destination for dog walkers. Photo / Neil Reid

"The very next day she came over to show me the van ... I didn't even get enough time to teach her how to even put oil in before she wanted to take off and go for a road trip," Anaherā said.

"She was so excited."

She lovingly remembered her little sister as "loud and proud".

"That is what I loved about her the most, what we all remember the most about her," she said.

"She was loud. And not just with her voice, but loud in the way she dressed, the way she held herself ... she was not a shy person at all."

Murder victim Ariki Rigby would have turned 19 two weeks ago. Photo / Neil Reid

Anaherā said her family were trying to stay as "positive" as they could as they try to rebuild their lives after the heartbreak inflicted by Ariki's killing.

For her, that meant doing all she could to share Ariki's story in the hope it could lead to those responsible for her death facing justice.

"We need them to be found; they are dangerous and they are still walking around," she said.

More than 700 people attended Ariki's funeral in Hastings last month.

Anaherā Rigby speaks during her sister's funeral in Hastings last month. Photo / Warren Buckland

Family members and everyday Kiwis also contributed to a koha which helped the family pay for the tangi and other associated costs with Ariki's burial.

Anaherā said the support provided to them was hugely appreciated and had touched the whole family emotionally.

"We love them all, everyone is so amazing with our whānau," she said. "It really helped us get through.

"I have had a lot of love and a lot of shoulders [provided] to give me good advice to carry on, things that help you get through grief."

• Anyone with information is asked to contact police on 105 quoting file number 220905/1265. Information can also be provided anonymously to Crime Stoppers on 0800 555 111.