Contaminated water linked to firefighting foam has been discovered at a petrochemical site in a second region.
The chemicals PFOS and PFOA have been found in both groundwater and surface water at the Marsden Point oil refinery in Northland, in testing done by Refining NZ - the company that owns the refinery.
One groundwater sample has tested at equal to the maximum recommended safe level for drinking water. The other samples tested lower.
It is not known how much lower the other test results are, or how many of them there are.
RNZ has asked the Northland Regional Council and Refining NZ to release the full test results.
The council said no one used the groundwater at the Whangarei heads for drinking.
Northland DHB indicated its medical officer of health had not been notified about the contamination.
Refining NZ said on its Facebook page it has tested shellfish in the harbour next to the refinery.
"The testing was carried out by an independent Australian laboratory, and the results received last week confirm that these compounds are not present in shellfish."
The contamination happened before PFOS was banned in 2006, it said.
"We can assure you that the talked about foams are not used at Marsden Point - they were replaced in the 2000s when concerns about the impact of these foams first surfaced."
PFOS have been on the international chemical hazards list since 2009 and were banned here in 2006. The man-made chemicals can last thousands of years and accumulate in the body. Health concerns have been raised worldwide, though the research into their impacts is inconclusive.
Refining NZ's online post was in response to confirmation last week of the first discovery of contamination caused by the petrochemical industry in Taranaki at four sites, plus the airport and two streams - some at above safe levels for drinking, although no one is known to use the water for drinking.
Northland Regional Council said all the surface water and groundwater samples were collected from within the refinery boundary.
Livestock did not drink the water, it said, and all the samples were well below the maximum levels recommended for recreational water which are much higher than for drinking water.
"The Marsden Point oil refinery is the only petrochemical site in Northland that is currently known to have used firefighting foams that contained PFAS," council group manager of regulatory services Colin Dall said in a statement.
The refinery has more than 150 monitoring wells, and said these enabled it to closely manage water quality.
However, routine petrochemical testing does not generally cover specialised PFAS tests.
Sixteen regional councils are part of nationwide investigations into contamination by the foam chemicals, called PFASs. These are also in products like Teflon and Goretex.