The two men killed in an abandoned Coromandel mine on Saturday died of carbon monoxide inhalation.
They were Kerry Alexander Murphy, 40 and Grant Christopher Wyllie, 49, both from Whitianga.
Significant amounts of chemical were found which is consisent with a drug lab, police told media at a press conference in Whitianga today.
There was no explosion in or around the mine, said acting Detective Sergeant Ross Patterson.
The mens' deaths were treated as sudden deaths as opposed to homicide and police were not looking for anyone else.
He said there were inherent risks to life in operating petrol powered generators in confined spaces.
He warned people to be diligent in operating generators under ground.
"This case shows the risks. Cooking controlled drugs imposes a high risk to themselves and those around them. The question has to be asked where the volataile waste products were being dumped."
He said there was no explosion at the mine. Police were informed by a woman acquaintance of the men that they were missing overnight. He understood they went in on Friday. The woman took police to the site where they were found.
It is understood they had been operating a makeshift P-lab in the mine, located in dense bush 10 kilometres west of Whitianga on the 309 Rd.
Investigators were yesterday filmed removing large quantities of chemical products from the dense bush-clad area, 10 kilometres west of Whitianga on the 309 Rd.
The area around the mine is covered in dense bush while the terrain is steep and boggy and the gorge and riddled with disused mine tunnels and mine shafts.
Police were alerted to "an incident" about 4.50pm Saturday.
A fire service spokesman confirmed fire appliances also attended a callout along the 309 Rd on Saturday evening but refused to reveal details of the job.
A Whitianga tourist operator, who declined to be named, said the winding 309 Rd was popular with tourists, but also had a reputation for drug activities.
"I know of some heavy-duty drug dealers who operate in that area and I'm sure the police have been aware of it for a long time. There are two landowners in particular who are involved in cannabis growing."
In 2006, two Coromandel Peninsula men were found guilty of growing $400,000 worth of cannabis in bush near the 309 Rd. In 2000 a police sting in the area snared cannabis plants, firearms, chemicals and equipment used in methamphetamine manufacturing.
Coromandel chief fire officer John Walker said none of his crew were involved in Saturday's callout but he did come across an "unusual sight" while driving along the 309 Rd at night.
"I was coming home from a golf staff function in Whitianga about 10.30pm [on Saturday] and as I was coming over the hill I came across three vehicles and there were guys in breathing apparatus. There were no reflectorised vehicles to say police, ambulance or fire and they weren't wearing uniforms. I just kept on driving. There was no way I was stopping on that bloody road at that time of night and there was nothing to identify it as a rescue service. I just kept going for my own safety."
The 309 Rd resident Brent Parker said the area was popular with pig hunters but disused mine shafts were a danger.
"I know on the Whitianga side there are a lot of mines all the way over . . . not far from my place . . . someone fell down a shaft a few years ago."
- Waikato Times