The alarm about the explosion came just before 3 am and several patrols were sent to the scene.
We still don't know what exploded, but it could be some form of pyrotechnics, it's unclear right now, says the police's press spokesperson Mats Eriksson.
There have been no extensive damage, or even any damage at all, he continues.
The area has been cordoned off for a technical investigation.
The incident is being investigated as reckless endangerment and a violation of the law on flammable and explosive goods.
