A series of mysterious "explosions" have been reported across west and north Auckland, but police are mystified.
Reports of loud ''bangs'' followed by houses shaking began about 5pm, in the Hibiscus Coast area.
Inspector Tony Edwards of police northern communications said police received reports of the bangs from the Herald Island - Greenhithe area about the same time.
More reports came in a while later from the Ranui - Scenic Drive area in West Auckland.
A Fire Service worker came in to work later and confirmed they had heard the noises in the Red Beach area, which is on the Hibiscus Coast.
Edwards said people had variously described the noises as sounding like gun-shots and loud explosions.
Police had checked with the Air Force, which has a base in Whenuapai, but turned out not to be not responsible, and neither was Paremoremo prison.
Lines companies had not reported any electrical disturbances and Geonet is not showing any tectonic activity in the Auckland area.
Arkles Bay resident Will Trayes said he heard the noises about 4pm.
His house shook with a "sudden, quick vibration" for two or three seconds and he heard a slight rumble similar to thunder.