A specialist report has confirmed the presence of asbestos at a run-down hot-pool complex near Kaikohe.
But it said people who had used the pools over the years were unlikely to have been at any risk.
Power company Top Energy bought the complex formerly known as Ginn's Spa as part of its plan to expand its geothermal power station at Ngawha.
It planned to renovate the complex, but closed it down after contractors reported asbestos materials had been widely used in its construction.
Top Energy chief executive Russell Shaw said the report had confirmed that asbestos fibres had contaminated some soil around the old buildings.
But the advice the company had had was that visitors to the spa would not have been in danger.
He said Top Energy was doing further testing, and considering its options.
The Waiariki Hot Springs over the road from the spa featured in the film Kaikohe Demolition will remain open.