"As a result of the injury, she has lost her leg," he said.
The woman was with a group associated with Black Power who drove to the Miriam St house occupied by a group connected to the Mongrel Mob.
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Mr Sutton said the investigation was making good progress and an arrest was made on Thursday.
"We are working with those involved, identifying what took place, identifying the people involved."
He said police were making sure there were no further confrontations or retaliation.
Extra resources, including police from Wellington, had been put on the investigation to help calm the situation, he said.
Police are still seeking a male driver, linked to the Miriam St house, who was driving one of the cars but fled the scene.
Anyone with information can contact the Wairarapa Police on 06 370 0300.
Alternatively, information can be passed on anonymously to Crimestoppers on 0800 555 111.