The Auckland Fire Service is trying to discover what is behind reports of a mysterious explosion heard over a wide area of the city on Wednesday afternoon.
The blast has been reported from Whangaparaoa to Lynfield and Blockhouse Bay.
The service says several of its staff heard a strange noise shortly after 4pm and there have been similar reports on social media.
A spokesperson described the noise as a rumbling such as that caused by a minor explosion or shockwave.
Members of the public are asked to contact the Fire Service if they have any information.