Police were called just before midnight to reports of an explosion in the building's stairwell, which quickly filled with smoke. No one needed to be taken to hospital, although several people suffered smoke inhalation.
The incident is classified as public danger destruction and a violation of the Act on Flammable and Explosive Goods.
"Work is underway to find the person or persons who caused the explosion. We do not believe it occurred naturally and believe that someone deliberately caused it," Martina Gradian, a police spokesperson, told Jönköpings-Posten .
At 5 a.m. on Saturday morning, the operation at the scene was completed.
