A large police operation is currently underway at the scene.
According to information to TV4 Nyheterna, a person armed with a knife is said to have uttered threats and attacked.
One of the injured is a school employee who was slightly injured in the arm, says police spokesperson Mats Eriksson to DN.
The police allegedly arrested a teenage boy on suspicion of serious assault, violation of the Knife Act and serious illegal threats, according to DN.