Eight cattle have died in the Waikato following a 1080 drop there.
1 NEWS has been provided with video from a concerned local showing a dead cow lying in the 1080 drop zone.
The Department of Conservation said it appears the cattle escaped their paddock through a broken fence line, wandering into the Mapara Wildlife Reserve where the poison was dropped.
"We have been working closely with the landowner concerned to confirm exactly what happened, and also to support them as any good neighbour would under these circumstances with the burial of the animals and feed for the others," DOC Operations Director David Speirs said.
Officials emphasised that the area is "one of their most important strongholds for kōkako (an endangered native bird) on mainland New Zealand" due to 30 years of pest control in the area, including the controversial 1080 programme.
The latest drop, focusing on the eradication of rates, possums and stoats, took place 6 September.
The cattle had been spotted in the drop zone during a pre-flight two weeks earlier, and the farmer who owned the animals was advised, officials said.
"No stock should ever be allowed within the pest control operational area," DOC said in a statement.
Department of Conservation staff say in the past month they've had their car tyres slashed and wheel nuts loosened.
Source: 1 NEWS
The animal deaths come at an especially sensitive time for the Department of Conservation, as anti-1080 activists step up protests.
The government agency has suggested many of the protestors have been influenced by fake news and misrepresented photos on social media.
With the increased publicity has come a torrent of online threats an abuse of workers, DOC threatened species ambassador Nicola Toki told RNZ yesterday.