An oil drilling rig off the coast of Taranaki has been shut down and will be evacuated after a 1.4m-long crack was discovered in the platform's structure.
Operator OMV says the de-manning and production halt are just precautionary measures, and says there's no risk to people or the environment.
OMV Australasian vice-president Gabriel Selischi says the crack was found in one of the platform's horizontal struts.
"The crack is about 1.4 metres long, on the third level down, and 4m below the waterline," he says.
He says the platform is very flexible, and has "a high level of built-in redundancy".
There are 34 staff based on the platform - 13 of them were flown off on Wednesday, and the remainder will leave Thursday and Friday.
"The issue is that we have bad weather approaching this weekend, and New Zealand also has a heightened earthquake risk, so we are taking a precautionary approach," Mr Selischi says.
The Maari oil field is 80km off the Taranaki coast, in water about 100m deep. OMV New Zealand is one of the country's third-largest gas producer, and holds shares in the Maui and Pohokura gas fields.