Six remote West Coast gold mines have been targeted by thieves on a crime spree.
The offenders stole gold and tools and reportedly caused hundreds of thousands of dollars of damage.
Police confirmed they are investigating six burglaries at separate mines, which all took place last Thursday night.
Tracy Billingsley, who is a partner at one of the mining sites, said the thieves took half a tonne of gold-bearing material and flipped over a new dump truck.
"As well, the thieves started our 38-tonne digger and smashed everything in its path and that included our trommels [gold wash plants] ... there was just a ton of damage," Billingsley told the Greymouth Star newspaper.
She said the trail of damage ran into the hundreds of thousands of dollars and believed at least five people were involved.
"They knew what they were doing. They broke into laboratories and container units looking for gold."
But they left behind the power tools.
Billingsley said she was speaking out to alert other mine owners that criminals were targeting West Coast gold claims "all over the place".
"It has got to the point where we will have to look at having people living on site permanently to avoid this happening again," she told the media outlet.
Police have asked anyone with information to call Crimestoppers anonymously on 0800 555 111.