One of the boys was mildly injured during the incident and the structure was undamaged.
The boys, ages 13 and 14, had constructed a bomb with a 1.5-litre plastic bottle. The boy nearer the explosion suffered light injuries to his face, and was taken by his family to a local hospital for treatment.
Police say this was not the first bomb the boys had made and detonated, but that they normally chose to set off the bombs in the woods. This time, they set off the explosive at 15:40 in the afternoon at the shopping centre's parking garage.
In October 2002, a 19-year-old man who lived nearby set off a homemade bomb inside the Myyrmanni shopping mall, killing himself and six other people, including three children. About 80 people were injured. His motive remains a mystery.