Holidaymakers may be sleeping in campervans contaminated with the toxic chemicals used to make methamphetamine.
National Clandestine Laboratory response team supervisor Detective Sergeant Rhys Wilson said portable P labs were on the rise, with police frequently finding them in campervans and other vehicles.
Once P cooks were finished with the vehicles they were likely to sell them, he said.
"The poor person that ends up subsequently buying this has obviously no idea of what it's been used for and what sort of contamination is in it."
This story is part of Broken Bad, RNZ's in-depth look at New Zealand's methamphetamine problem. Read more here.
Solvents, acids and caustics were often found in the clandestine labs, he said.
The chemicals were "pervasive and cause significant contamination."
"Houses are more often checked for meth contamination but things like mobile homes ... aren't usually checked for contamination and tend to pass through quite a few pairs of hands."
A meth lab environment can cause heart, breathing and skin problems.
While some cooks manufactured the class A drug in vehicles, others contaminated vehicles by using them to store or transport chemicals and meth cooking equipment, Mr Wilson said.
When police found stolen vehicles that had been used by P cooks they alerted insurers who could have the car decontaminated or destroyed.
But that did not help people who bought contaminated vehicles that police had not had contact with, Mr Wilson said.
Some private meth testing companies said they were increasingly being asked to test vehicles.