About 120 staff had to be evacuated from Defence Force headquarters in central Wellington after a suspicious package shaped like a grenade was discovered.
The parcel was detected by staff in the mailroom when it went through a scanner at 7.55am on Tuesday.
The bomb squad was called and a robot bomb detector put on stand-by.
The Defence Force evacuated the west wing of the building for about 90 minutes until it was confirmed that the package was harmless.
Squadron leader Kavae Tamaraki says it is not out of the ordinary for objects in the mail to raise suspicion.
The package turned out to be a plaque for a staff member leaving the organisation, he says.