One person was transported to Wellington Hospital in a status one [critical] condition.
A Cambourne resident told the Herald she was aware of the police operation.
A friend had seen a large police presence on Grays Rd, near the entrance to Cambourne Walkway. She counted about seven police cars and several ambulances.
Police said Pauatahanui and Porirua residents in the area will see an increased police presence while the investigation continues.