The police had to move out after fireworks were fired inside the canteen at Bjørnholt upper secondary school in Oslo.
No one was injured in the incident, and no one was arrested, police told NTB news.
The police received notice of the incident at 13.50 on Monday and sent several patrols to the site.
“For a long time, it was a difficult and demanding situation because of many students who disturbed the police” said operations manager, Marita Aune, in Oslo police district to NTB.
It was not necessary to summon the fire service she said.
Bjørnholt High School, located in Søndre Nordstrand district south of Oslo, was one of the first schools in the country to introduce access control for all pupils and employees.
© NTB Scanpix / #Norway Today