The explosion occurred at 5 a.m. Sunday at a villa on Älgö, a peninsula in the archipelago on the outskirts of Saltsjöbaden.
"There, an object exploded and caused damage, especially to the front door. At the time, a whole family was in the house, but no one was injured," the police write on their website.
A preliminary investigation into endangering the public has been initiated.
"The property owner is one of those who raised the alarm. I can't say whether he was in the property or noticed it in any other way, says Niklas Berglund."
The police would not comment on whether there are any suspects in the case.
"At this time, the motive for the explosion is unknown," the police write.
