On Christmas Day they said they were looking for a man who had thrown an object through the window just before the fire. But now they say they cannot confirm this information, which they got on the scene from a witness. And local SVT channel had reported a witness saying someone had been seen near the entrance with a bottle of petrol.
The head of the investigation, Lars Franzell, says to Swedish Radio News the oral testimony, taken by a commanding officer on the scene, was in the midst of "chaos" and they have not been able to confirm the claim.
Police have not ruled out the possibility of an attack, but are also looking into other causes. They will need to use dogs to search the wreckage for traces of petrol or other inflammable liquids.