The Armed Offenders Squad helped police secure the property, Mr Kelly said.
"Again, because of the risks posed not only to the public but to our staff and the offenders themselves, when firearms are believed to be present we need to take certain precautions to ensure the safety of all those involved.
"Due to the high level of planning the property was able to be secured without incident and the road reopened shortly after 7.15am. A scene guard is currently in place and will remain there to assist in the securing of the property as it is searched by the inquiry team."
A police spokesman told APNZ he saw a room "totally full" of cannabis and another half-filled with dry cannabis. He said there were two other rooms but he was unsure of how much of the drug was in those rooms.