The bomb disposal unit personnel arrived at the site shortly before 2pm and after inspection confirmed the item was a realistic-looking inert replica German stick grenade.
Customs were allowed back into the building about 3pm, and staff would continue to examine the rest of the container today, she said.
A Customs spokesperson said the container was sent from the United Kingdom and destined for Tauranga, and the importer's documentation stated there were antique firearms inside which was
the reason the container had been examined and X-rayed.
The spokesperson said Customs was still investigating the scare and were yet to decide whether any action would be taken against the importer for failing to declare this item.
The inert grenade was being held in Customs' inspections facility and whether it would be returned to the importer along with the rest of his household items was still to be decided, she said.
Three men from NZ Van Lines said they were loading items from the container onto one of their company's trucks when Customs staff using a mobile X-ray machine made the discovery.
They praised Customs personnel for their quick action in evacuating everyone from the area.
The three men appeared unfazed by the drama.
One of the trio said inside the container along with household items was a couple of other war-time memorabilia including some "old muskets".
"It's a bit more interesting start to my usual working day," he said.
Tauranga-based chief Customs officer Jamie Hickey said it showed how important it was for people to correctly declare the contents of their containers.