People are being urged to take care in areas of the Hunua Ranges where toxic 1080 bait has been laid.
The Auckland Council said the first application of 1080 in the Hunua Ranges area was complete, and the parklands were expected to reopen later this week.
In the last few years, possum and rat numbers have increased significantly in the area, and this was having a severe effect on the health of the forest and threatened species, like kokako, that live within it.
To target these pests, 1080 bait was applied to a block of the 21,000 hectare area last Friday.
Another block was also treated, with non-toxic pre-feed bait to familiarise pest animals with the baits.
Auckland Council's Biodiversity Manager Rachel Kelleher, said the operation was now past the half-way point.
"The operation is progressing well, we are starting to see evidence of the toxin at work and are monitoring breakdown of both bait and possum carcasses to inform our caution period.
"Staff have completed the initial requirements of our track clearance programme which has also been audited by the Auckland Regional Public Health Service."
Now, Ms Kelleher said it was important for dog owners to think carefully about bringing their pets into, or near, the operational area.Any dogs that were brought into the area should be supervised at all times, she said.
Ms Kelleher said once the park re-opened, visitors must remain aware that they were in an area recently treated with 1080. She said dogs and young children were particularly at risk from 1080 poisoning.Those who chose to bring their dogs to areas of the parks where dogs were allowed, or near to the operational area, should supervise them closely.
Dog owners should also consider muzzling their dogs if they are off-lead.
Meanwhile, Watercare's Wairoa and Mangatawhiri dams remain out of service until a stringent water testing programme was completed, and approval had been given by the Medical Officer of Health.
So far have no 1080 has been detected in the water supply.
Negative results were also being returned from the cultural and private property water testing programme, which involved working with iwi and private landowners to monitor waterways flowing from the operational area.
The next and final stage of the operation would be in 7-10 days, depending on the weather.