"We believe at this stage that the drug may have been smoked in the property, rather than manufactured, which means levels are likely to be quite low," he said.
"We expect final results in the next fortnight and will then make a decision on next steps - for example, cleaning and repairing the property."
Mr Bosch said they were working closely with potential buyers throughout the process.
HNZ manages about 69,000 properties, and .009 per cent of their total housing stock was found to have been used in methamphetamine production, he said.
"Our staff are trained to spot the signs of methamphetamine manufacture and work closely with police if a laboratory is suspected," said Mr Bosch.
Envirocheck office manager Jasmine Pruden said telltale signs that meth had been manufactured or used in a house include a "chemical smell" or "chemical discolouring" in places like the laundry or down window sills where chemicals have been tipped out.
Other signs to watch out for were dodgy wiring and plumbing, fire alarms that had been removed or missing light bulbs.
However, she said some cooks and smokers were "smart enough to clean up after themselves". "Sometimes you can walk into a property and it can look amazing, but it can be fully contaminated," she said.
"People are starting to be more aware that people know of these usual signs."
Real estate and property management companies around Wanganui said they did not have an issue with contaminated houses.
Manager of The Watsons in Marton, Phillip Mullins said: "I've never come across that in 15 years."
Chemicals from meth residue can be inhaled, ingested, or absorbed through the skin.
Acute exposure can cause shortness of breath, cough, chest pain, dizziness, lack of co-ordination, chemical irritation, or burns to the skin, eyes, nose and mouth. Death was possible if the chemical was particularly toxic or the person was vulnerable.
Less severe exposures can bring about headaches, nausea, dizziness, fatigue or lethargy.
Childhood exposure could damage organs and bring about violent behaviour as well as seizures and hypertension.
