The incident occurred on the second floor of a part of the school where there are student lockers.
The detonation was detected by an automatic fire alarm.
- The rescue service is sent there, when they arrive and are to investigate what has triggered the alarm, they see that there is damage inside, and an odor that indicates that something has detonated.
That is when you call the police, says Rickard Lundqvist at the police.
It is currently unclear what has detonated.
No one was injured and no fire broke out.
The police's national bomb squad is on site at the school.