Loud explosions heard at Muriwai beach on Friday evening was the Defence Force detonating a "small cylindrical object".
Multiple residents heard loud noises about 9pm, not long after a water rescue took place at the surf beach, where a rescue helicopter was dispatched.
Police confirmed the incidents were unrelated and that a controlled detonation of an unidentified object took place.
A police spokesman said police were called in to help the Defence Force at 3pm after a "small cylindrical object" was found at Takapuna, on Auckland's North Shore.
Police couldn't be specific about what the object was.
The object was taken to the bombing arena at Muriwai beach hours later, where it was detonated in a controlled explosion, the spokesman said.
The Defence Force has been contacted.