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A former police negotiator is confident a grisly homicide investigation under way in South Auckland will be solved - but those responsible may already be overseas, he says.

Ex police crisis negotiator Lance Burdett says considering the size of New Zealand, he is "quite hopeful" that officers will be able to solve the case.

"It's a small country. We have very few unsolved homicides, we have a handful of them, you can count them. So I'm quite hopeful."

However, depending on when the original incident or incidents occurred, there is a chance that those responsible are now living outside of the city or even overseas.

"But again, you leave a trail...somebody will brag," Burdett said.

Police announced a homicide investigation was under way after being alerted to what was described as a "discovery" at a property on Moncrieff Ave, in Manurewa, last Thursday.

Counties Manukau District crime manager, Detective Inspector Tofilau Fa'amanuia Va'aelua, confirmed human remains had been found after people living at the house had brought "unowned property" back home.

"From our inquiries so far, we can advise the occupants of the address are not believed to be involved in the incident."

The latest development is that the unowned property brought back home was a number of suitcases that were purchased as part of an auction of a storage locker that had been left abandoned.

Newshub said a trailer-load of items was picked up from a storage unit in South Auckland that had been won by the family, according to a police source.

Police have not officially confirmed those details, however.

Tofilau said at the time that the priority is to confirm the identification of the deceased so that the full circumstances behind the discovery can be established before advising next of kin.

"Given the nature of the discovery, this might take some time."

Former police crisis negotiator Lance Burdett. Photo / Todd Eyre

Burdett, who was a police officer for 22 years, acknowledged how difficult the situation will be for everyone involved including those officers and any ambulance or fire crews initially called to the site.

"When you attend a grisly scene like that, you can never erase it from your memory. It's a hell of a time.

"What Police and most first-responders do is get stuck in and not focus on the details. They focus on the process of what they have to do.

The hunt to find who is responsible

"It's all about finding who is responsible. When you have something like this, the number one goal is to find who's responsible and it just motivates you - it's used as a motivation rather than a negative: 'We must find who is responsible'."

Burdett said investigating officers will be looking closely at the evidence they have at the moment and then work backwards - including going back to the storage facility and examining it and everything associated with it carefully.

"There will be a record somewhere...of who rented it. That'll be the focus."

Authorities would be looking at records, any archival security footage and members of the public who have a storage locker at the same facility, he said.

"There are some good lines of inquiry. Things like this, when you leave evidence - the more evidence left, the greater the ability [to solve the case].

"Things will turn up - people always want to help in these cases. Somebody will remember something."

Burdett has had his fair share of grisly cases and harrowing shifts; such as the night he was called to an accidental balcony death and a near-miss at a train track, before walking in on an offender in the middle of dismembering a body - all within a space of about four hours.

"It never leaves you. It stays forever," he said.

Can you help? Anyone with information is urged to contact Police immediately on 105 or CrimeStoppers anonymous on 0800 555 111