More households near Ōhakea Air Base have discovered their water supplies are contaminated with chemicals from a toxic firefighting foam.
Seventy-four groundwater samples have recently been taken around Ōhakea, up from 26 samples taken in December last year.
Six water wells serving eight properties have returned results with levels of foam chemicals at or above the drinking water guidelines.
The contamination was newly discovered in two of those wells.
Ministry for the Environment chief operating officer Claire Richardson said there was no serious health risk, but it was being vigilant.
"We are working directly with everyone affected around Ōhakea, to provide them with advice and support tailored to their individual needs," she said.
Ms Richardson said alternative water supplies - such as bottles or tankers - remain available to residents.
"So they've been provided with the results, they've had conversations with officials to explain what those results mean and our focus is ensuring that they have the support and access to an alternative drinking water supply."
Studies have linked the toxic foam - a fire retardant used by the Fire Service, Defence Force, Marsden Point oil refinery and airports - to testicular and kidney cancer, tissue damage in the liver, and a weakened immune system.