The Armed Offenders Squad has swarmed around Southdown Lane in Penrose, Auckland.
Police were executing a planned searched warrant involving a wanted man this afternoon.
The operation had been completed and five people were currently in custody, Counties Manukau West area commander Inspector Naila Hassan said.
At 1.39pm a witness said a woman had been arrested by police after four other people were arrested earlier.
The police helicopter was seen hovering over the scene off Great South Rd, a witness said.
The Armed Offenders Squad has been aiming guns what looks like an industrial building on the road, a witness said.
The road was closed for several hours during the operation but had reopened at 2.25pm.
Fire and Emergency New Zealand (FENZ) were seen setting up a shower on the road, another witness said.
A FENZ command unit arrived 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.
"I was coming back to work when I noticed the road was closed and there were cops with guns," a witness said.