A post-mortem has revealed that two men found dead in an abandoned mine on the Coromandel peninsular died from carbon monoxide poisoning.
The bodies of Kerry Murphy, 40, and Grant Wylie, 49, were found on Saturday in the shaft on The 309
Road near Whitianga.
Police believe the mine was being used as a clandestine drug laboratory and have found drug equipment and chemicals, along with a generator and a gas bottle.
Acting Detective Senior Sergeant Ross Patterson says the deaths should serve as a warning that operating petrol-powered engines in confined spaces puts lives at risk.
Mr Patterson says cooking controlled drugs such as methamphetamine poses a high risk to people and others around them.
Mr Patterson says there are lots of drafts and abandoned mines in the area but it would be impossible to search them all for suspected drug labs because the terrain is so rugged and dense.
He questions where the pair may have been dumping toxic waste produced from methamphetamine manufacture.
Police are not looking for anyone else in relation to the deaths and the matter has been referred to the Coroner.