Police spokesman Dan Larsson said investigators had found evidence that indicated the fire was started by arsonists.
The building destroyed in the fire was more than 100 years old. Police say that they so far do not have any suspects for the crime.
The alarm was sounded at 3 am on Saturday. A total of 80 firemen were called to the scene. Emergency services say that 10-15 apartments were destroyed in the blaze, as well as two restaurants and a shop. No people were hurt in the fire.