Head Hunters at the 2015 memorial for Connor Morris in Auckland.

A meth turf war, if one hasn't already started, is inevitable in New Zealand according to a leading criminologist.

One gang member is missing, the Head Hunters are continuing to expand into new areas, particularly in Waikato and Christchurch, and police are seizing vast amounts of drugs, cash and paraphernalia.

"Gangs aren't bound by law. They have to work out their own laws," said Canterbury University professor of sociology and criminology, Greg Newbold.

CHRIS SKELTON/STUFF Members of the Head Hunters, friends and family at the funeral service of Connor Morris in Auckland, in 2015.

To achieve those ends and establish a new monopoly, gangs employ unregulated tactics, standover moves, rip-offs, theft and deceit. Violence.

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WARWICK SMITH/FAIRFAX NZ Police set up at the Hokio Beach Rd bach at the centre of a police investigation into a missing gang member.

"This kind of warfare that appears to be breaking out with the gangs is pretty much inevitable," Newbold said.

Nomad gang member Palmiro George MacDonald, 36, from Horowhenua, is officially missing, according to police, and gang sources say something's got to give.

In the world of methamphetamine manufacturing, distribution and supply, it pays dividends to keep your mouth shut.

Just what is happening on the ground, in small towns, in city suburbs, or pads, isn't entirely clear, but there are signs.

A previous report featuring MacDonald described him as having a "staunch attitude around gang connections" and entrenched views.

Central District Detective Inspector Ross McKay, on Tuesday, said police were concerned for MacDonald's wellbeing and rumours were circulating in the community. The disappearance warranted a major investigation, he said.

"We are keeping an open mind at this stage about what might have happened to Palmiro, however we can't rule out the possibility of a sinister element in his disappearance."

Senior police have shed some light in recent months.

One gang keeps cropping up. Head Hunters.

RAPID EXPANSION

The gang is expanding, according to police and underworld sources.

In January, Organised Crime Detective Superintendent Virginia Le Bas said the Head Hunters' success hinged on operating a business model, its organised structure and reporting to Auckland.

Gang sources, too, have confirmed the rapid spread of the Head Hunters.

Le Bas said the Head Hunters operated strategically and they have connections with Asian gangs in organised crime.

A Mongrel Mob source said the rival gang was moving fast.

"It's pretty massive how fast they are rolling out across the country, but you know something's gonna give soon."

But, if a full scale turf war were to break out, the fallout is likely to affect the three main gangs, Mongrel Mob, Head Hunters and Black Power.

In one incident, which police refused to discuss, shots were fired at a group of Head Hunters newly arrived in a Waikato town.

Now, MacDonald is missing, a bach has been razed and tensions are simmering.

Newbold​ said a gang war was inevitable if one group attempted to expand.

"There will be cooperation between agencies and also between different producers for different geographic portions of the market share.

'THEY'RE CLEVER MEN'

For many years the Head Hunters were centred in and around Auckland but there are signs of aggressive expansion.

Newbold said the gang, which started as an Auckland street movement in the late 1960s before morphing into a bikie outfit, was expanding.

"Now it looks like the Head Hunters have a deliberate and organised policy of expansion and, as part of that, they are encroaching on a market share.

"This type of violence is more serious and more sophisticated.

"The leaders are very bright. They're clever men."

One under-reported aspect of the methamphetamine world was the close involvement of Asian gangs, who act as the importers of precursor chemicals and the finished product, the professor said.

After this, the drugs were sold to the gangs for production and distribution.

Newbold said the expansion was making North Island inroads, to Palmerston North, Tauranga and Taranaki and, in the South Island, Christchurch and Dunedin.

GANG ASSETS

A March police intelligence summary report said almost half a billion dollars in suspect assets had been investigated since 2009.

Intelligence summaries say the country's asset recovery units, in Auckland, Hamilton, Wellington and Christchurch, investigated 3045 cases since 2009 involving assets worth $475 million.

Assets under investigation include 1124 bank accounts worth $78m, 564 houses worth $273m and 71 farm properties worth $49m.

Police opened almost 1000 cases, many linked to organised crime, a report says.

Methamphetamine offending was linked to 364 cases, involving a total sum estimated at $138m.

And the Head Hunters, the gang once associated with Sir Paul Holmes's step-daughter, Millie Elder-Holmes, and her slain boyfriend Connor Morris, are one of the top distributors of methamphetamine in New Zealand.

One Mongrel Mob source, earlier this year, had this to say about the rival group.

"We see them setting up in the hood - we just gonna let it lie for now.

"But they gonna push it soon and something will go down and it ain't gonna be pretty," he said.

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