The Armed Offenders Squad is swarming around Southdown Lane in Penrose, Auckland, as police execute a search warrant.
At 1.39pm a witness said a woman had been arrested by police after four other people were arrested earlier.
The police helicopter is also hovering over the scene off Great South Rd, a witness said.
The Armed Offenders Squad has been aiming their guns what looks like an industrial building on the road, a witness said.
The road has been closed by emergency services.
Fire and Emergency New Zealand (FENZ) is now setting up a shower on the road, another witness said.
A FENZ command unit arroved on site around 1.30pm.
Another witness said earlier it appeared a man had been bitten by a police dog and was sitting bleeding under a tree.
Four people wearing handcuffs have been taken out of a building by police, he said.
Six 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 were cops with guns,” a witness said.
At 12.46pm police appeared to be searching for another person, the witness said.