The missing weapons were not police firearms; they were being held as exhibits or had been handed in for destruction.
The embarrassing loss occurred while gun owners are surrendering military-style semi-automatics (MSSAs) and assault rifles nationally as part of a Government buy-back scheme following the Christchurch mosque shootings.
MSSAs and assault rifles were banned in rapid law changes after the March 15 shootings. An amnesty for handing in the weapons is operating until the end of September.
When the buy-back was announced, Police Minister Stuart Nash sought police assurance they had strong processes for handling the firearms. Police said at the time they were confident they could manage the collection of the guns.
Following the alleged station burglary, Nash has sought a new assurance.
Police Commissioner Mike Bush has demanded an investigation into how Harris was allegedly able to get into the Palmerston North station. Stations' firearms security nationwide is also being reviewed.