The incident occurred in the early hours of Friday morning at the restaurant and nightclub Babel in the southern Swedish city.
“We have ascertained that there was an explosion and there is damage to the front of the building,” Magnus Lefèvre from the regional police force told TT.
The restaurant and club was closed at the time of the explosion and there are no reports of any injuries in the blast.
Several loud bangs were reported by local residents shortly after 00.30 am, but police did not find any other areas affected by a blast.
Bomb technicians have surveyed the building and currently do not believe the blast was caused by firecrackers. The technical investigation continued through the night.
“It is some form of explosive material that was detonated, but the bomb technicians couldn't say what it was,” Lefèvre said. “Next we'll look at whether there was any known threat against the restuarant or any of its employees; for the moment we are not aware of any such threat.”
In October last year, the same nightclub was hit by an explosion, which caused damage to the front of the building.