The Armed Offenders Squad is swarming around Southdown Lane in Penrose, Auckland, as police execute a search warrant.
The police helicopter is also hovering over the scene off Great South Rd, a witness said.
The witness said it appeared a man been bitten by a police dog and was sitting bleeding under a tree.
Four people have been taken out of a building by police wearing handcuffs, he said.
ix police cars are in attendance as well as St John.
A police spokeswoman confirmed the AOS was executing a search warrant.
"I was coming back to work when I noticed the road was closed and there was cops with guns," the witness said.
At 12.46pm police appeared to be searching for another person, the witness said.