A dozen contaminated LPG supplies have led industry leaders to put an investigation team together.
The problem has caused home heating systems to fail, depriving people of hot water and necessitating repairs of damaged components.
Only 12 out of 115,000 customers had reported problems, but the Liquified Petroleum Gas Association (LPGA) viewed that as 12 too many.
It set up a team to investigate the problem.
LPGA executive director Peter Gilbert said he had become aware of the problem last year and so far the components of six damaged home LPG supplies had been tested.
However, the source of the contamination had still not been found.
Mr Gilbert said there would be more tests and the investigating team would continue until the source was found.
"We will work through until we come through with an answer," he said.
"They are very small quantities we are talking about, millilitres," he said.
The contaminant is one of a class of chemicals known as phthalates.
A study at George Washington University in the United States capital found some phthalates could damage the reproductive system and may lead to infertility.
The report said the American government had prohibited the use of phthalates in the manufacture of children's toys in 2008.
However, Mr Gilbert said the contaminations would have no health effects.
"The substance is always contained within the LPG or it is contained within the appliance itself, so the customer never comes into contact with it.
"It is not an issue for customers."
There have been no reports of health incidents in New Zealand.
LPG is often known as butane or propane, and is used in aerosols as a refrigerant and in home heating, vehicle propulsion and barbecues.
The phthalate contaminants are commonly used in plastics and rubber to soften them and make them flexible.