A bomb squad has identified a mysterious object found at a beach south of Whangarei as a navy training mine.
Police called in the squad after a member of the public found the mine rolling around in the surf at Ruakaka Beach about 9.30am on Thursday.
Lieutenant Commander Greg Camburn said it was one of two that went missing after a diver training exercise in rough weather in late June in Tauranga Bay.
He said the mines are usually recovered after training, are not live and there was no risk to the public.