A professional chemical decontamination expert is urging prospective homebuyers to check for methamphetamine.
This after Housing New Zealand (HNZ) figures show an increase of more than 700 percent in contamination.
Site Decontamination Services owner Brent Nicholson says his company's workload is growing.
Mr Nicholson says landlords should check on their properties and vet their tenants, and recommends homebuyers get a test done to determine whether the house has been used as a meth lab.
He says the signs are "invisible" without testing being done and could be harmful to people.
It costs between $600 and $1800 to test whether a property has been contaminated by methamphetamine, but making the house liveable again can cost up to $30,000.