An Upper Hutt high school went into lock-down this afternoon after a teenager was seen walking through the grounds with what appeared to be a pump-action firearm.
Police have since recovered an imitation firearm and students, parents and teachers at Heretaunga College have been allowed to enter and leave the school.
Senior Sergeant Marc Clausen said police received a report that a teenage boy, dressed in a grey hoodie, was carrying a pump-action firearm through the school grounds about 2.40pm.
He said streets around the school were cordoned off while about 20 police staff, including armed officers, and two police dogs searched for him.
Students were told to remain in the classrooms and keep out of sight, away from the windows.
Mr Clausen said a BB gun-type imitation firearm was found in a residential property across the road from the school a short time later.
"Inquiries are continuing to try and locate the person who had the firearm. The school has all been let out and we've stood all the police staff down, apart from those making those inquiries."
The property where the imitation firearm was found was not linked to the weapon, Mr Clausen said.
"We're just making inquiries as to how it got there and who might have dumped it there."
It was not known if the teenager was a student of the school.
"He wasn't recognised - his face wasn't seen."
Police had a possible suspect in mind, but would not know for sure until they had found and spoken to him.
The teenager was described as about 1.72m tall, weighing about 100kg and wearing a grey hooded sweatshirt.
He was not seen pointing the firearm at anyone, and had not spoken to anyone.
"He was last seen walking around the school grounds, then they lost sight of him."
The firearm would be examined forensically and a decision on charges would be made once police located a suspect.
Mr Clausen said police were pleased with the school's response.
"The school did really well with their lock-down procedures and did everything that you could have asked of the school, so it was well-managed."
Police earlier asked the public to stay away from the area and for parents collecting students to delay that. However, the public was now free to come and go.
