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Customs officers alerted police to the find after spotting the weapons, which appeared to be armed, and ammunition during a routine X-ray of the container.
The items were stored in boxes inside the container, which had come from China.
An area around the Fryatt St container yard where the container was being examined was cordoned off for about 30 minutes around noon until officers confirmed the cargo of munitions had been disarmed.
Sergeant Chris McLellan, of Dunedin, said the bomb squad was dispatched from Christchurch as a precaution to ensure no live explosives were inside the container.
The squad arrived to examine the container's contents about 6pm.
An initial police assessment had found the grenades and mortars, while appearing to be authentic weapons, were most likely imitations, while the .50 calibre rounds were real but the working components of the bullets had been removed and the caps replaced.
Other suspicious items, including an "unusual" collection of knives, were found in the container.
Police, Customs New Zealand and Port Otago were tracing the container's movements, including the ultimate destination and use of the goods.
Police were assuming the items were for personal use.
It was unclear yesterday whether the correct paperwork for the items had been filled out.
A New Zealand Customs Service spokesman referred queries to the police.
Customs' main concern yesterday was public safety at the scene, he said.