Police said in a statement this morning they had arrested Harris, who was sought after a burglary at the Palmerston North police station on Thursday morning.
"Harris was arrested without incident in Palmerston North in the early hours of Saturday morning," police said.
"He was identified by a member of the public in the central city and police were immediately notified."
The 11 firearms, which were unaccounted for after the burglary, were still being sought, police said.
"Police are actively pursuing a number of lines of inquiry to locate them."
Inspector Sarah Stewart, Acting Central District Commander, said locating the firearms continued to be a high priority.
"While an arrest has been made, it is very important that anyone with information which will assist us in locating the firearms makes contact with us.
"Anyone with information can contact the Palmerston North Police directly on 0800 351 3600.
"Information can also be provided anonymously to Crimestoppers on 0800 555 111.
"I would also like to thank this member of the public for their alertness and prompt actions in notifying police last night," she said.
Police Minister Stuart Nash is demanding an explanation from police about the theft.
The guns were not police firearms but were being held as exhibits or had been handed in for destruction.
The embarrassing blunder occurred as gun owners are surrendering military-style semi-automatics (MSSAs) and assault rifles around the country as part of a Government buyback scheme which followed the Christchurch mosque shootings.
Nash said yesterday afternoon he had "grave concerns" about the alleged burglary.
When the buyback scheme was announced, he had sought assurances from police they had strong processes for handling the firearms, he said.
Police said at the time they were confident they could manage the collection of the high-powered weapons.
"I have now sought fresh assurances from the Commissioner that all stations and firearms-handling processes are secure and fit for purpose, and that firearms are stored safely, whether they are crime scene exhibits or otherwise," Nash said.
Police Commissioner Mike Bush has asked for an investigation into how Harris was allegedly able to get into the police station.
The investigation would also require an immediate audit of security around firearms at all police stations nationwide.
Military-style semi-automatics (MSSAs) and assault rifles were banned in an urgent law change which following the shootings at two Christchurch mosques on March 15.
While MSSAs and assault rifles guns are now illegal, an amnesty is in place until the end of September.
