An object has been thrown at a residential building in Sollentuna and exploded, according to the police. Several people called in and alerted about hearing bangs in the area around 21.40 on Wednesday.
A door has been damaged in connection with the incident, but no one is injured.
There is no fire or smoke development at the site, says Thomas Skans at the rescue service.
A preliminary investigation into reckless endangerment has been initiated. A number of people are to be questioned, but no one is currently suspected of a crime, according to the police.
The police are working to gather more information through, among other things, door-to-door inquiries, control of individuals, and inventory of surveillance footage in the area.