UPDATE 8.10am:
The operator of a Northland geothermal plant has denied reports of an explosion and 30,000 litre gas leak this morning.
Northern fire communication shift manager Nicole Bernard said more than 30,000 litres of gas had leaked at the Ngawha geothermal station in Kaikohe, causing an explosion just before 6am.
``We received a call at 5.45 to an explosion at the power station. When the Fire Service arrived they transmitted a third alarm and stated that 30,000 litres of methane gas [was] leaking on site.''
However, Russell Shaw, chief executive of the station's operator Top Energy, said the reports were false.
The site holds pentane, not methane gas.
``There's been a gas leak, there's been no explosion. We have a safety valve on our pressure vessels.
``That safety valve operator sensed over-pressure and ... about 5.30am this morning, the operator, who's the only person on site, shut the station down and evacuated the station.''
``He called the Fire Service who then did a controlled re-entry on the site and to test to see if any gas had been released.''
The Fire Service had been carrying out tests since 6am and were due to leave the site by 7.30am, Mr Shaw said.
``They've found at this stage no release. The station holds 30,000 litres [of pentane gas] so if it had gone up in a big puff of smoke than 30,000 would have been released, but at this stage they've found nothing.
``That is the latest report that we've had from our plant manager.''
The safety valves had never gone off before and it was unknown what had caused it to happen today, Mr Shaw said.
``At this stage we don't know and as a precautionary process, because the gas is highly flammable, if we have a release, we evacuate our operators from site and we go through this process of a controlled re-entry.''
Mr Shaw told TVNZ that the site was relatively close to the Ngawha village settlement and the company would be working with them to let them know what had happened.
Residents were not in any danger he said.
A full investigation would be carried out to determine why the safety valve had gone off, he said.
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The Fire Service said it received reports of a gas leak at Ngawha geothermal power station near Kaikohe about 5.45am today.
There are reports Methane gas is leaking following a explosion. A safety valve was released and the system worked as designed.
Firefighters who went to the plant found 30,000 litres of methane gas was released on the site and were working with staff at the site.
The plant has been shut down and it is unsure how long it will remain closed.