Aviation businesses were evacuated from Ardmore airport near Auckland on Tuesday after bombs were found in a drain.
At least 130 practice bomb heads have so far been pulled from the collapsed drain on Harvard Lane near the airfield.
The bombs, used in the 1970s for target practice, were discovered by airport staff about 11am on Tuesday.
Fears about the site's proximity to a fuel tank prompted police to cordon off the site and evacuate aviation businesses nearby.
However, an armament technician with the Air Force says the bombs pose no risk to the public.
Corporal Michael Hartley says the bombs are no longer live. A metal detector is being used to ensure that the site is completely clear.