Hoax bomb threats made to two Northland schools may be linked to similar incidents at other New Zealand schools.
Kerikeri High School received a phone threat just before 11.30am yesterday, which was a hoax, but was treated seriously.
Kaitaia Intermediate School principal Sue Arrell said the school office also got a hoax bomb call yesterday.
Ms Arrell said police and security looked over the school, found nothing alarming and everyone carried on.
She said there was no evacuation and she suspected it was just another manifestation of threats made to other New Zealand schools the previous day.
Calls of "a concerning nature" had been made to 27 schools this week, police said yesterday.
Several schools received bomb threats on Wednesday and several more also reported receiving bomb threats yesterday.
In Kerikeri, alarms were activated and all 1550 students evacuated onto the sports field next to Kerikeri Domain, where they were lined up by year and form room while teachers checked all were present.
They then waited in the shade of nearby trees until police gave the all-clear about 20 minutes later.
Deputy principal Daniel Wise said the school called 111 immediately and police were quick to respond.
"We always take these things seriously for the safety of our kids, so we chose to evacuate ... The kids were great," Mr Wise said.
Kerikeri Police Sergeant Phil Le Comte said the evacuation was impressive, with students already on the field when officers arrived.
Students were allowed back to class around noon after police spoke to staff at the school and liaised with their district command centre in Whangarei about similar events elsewhere in Northland and around the country in recent days.
Mr Le Comte said he couldn't praise the high school enough for its quick response and evacuation.
Police were working to trace the origin of the calls.
Fire Service's Far North fire commander Allan Kerrisk also attended the Kerikeri High School evacuation. There had been a spate of similar incidents around the country but yesterday's were the first he knew of in Northland.
It is understood the threats are pre-recorded and made using an automated telephone system.
The threats vary but are believed to include a bomb hidden at the school and a gunman on the roof.
Former Far North police area commander Chris Scahill, now a superintendent in Wellington, said the calls could be computer-generated and come from overseas.
"We are very aware of very similar incidents occurring around the world, in particular the United States, UK and recently Australia," he said.
Tracking the calls back to a particular location or person could be be challenging.
If they originated overseas New Zealand Police would have only limited ability to prosecute.