A large-scale 1080 pest control programme across the Hunua Ranges, south-east of Auckland, has suddenly been suspended.
A conservation group opposing the drop - The Friends of Sherwood Trust - won a temporary injunction in the Environment Court, about the same time as non-toxic cereal pellets were being dropped across the ranges last week.
The trust is worried that 1080 could fall into the water supply.
The non-toxic pellets used in the precursor drop are designed to entice pests like rats, possums and stoats with a taste of the bait before the toxic version is dispersed.
The drop of actual 1080 poison over the Hunua Ranges was expected to take place by the end of this week, weather dependent.
But the Environment Court ruling has put that on hold, while a full hearing is due this Thursday.