It is to be able to find out what has happened, says the police's press spokesperson Evelina Olsson.
She states that there are among other things question marks regarding a previous statement from the police that "someone is supposed to have thrown in a burning object" in one of the apartments.
There are question marks regarding the sequence of events which we are now checking on.
25 people who were in the house had to temporarily leave their homes. A man who got out on his own was taken to hospital for a check-up.
We have had police on site to talk to him, says Olsson.
The fire broke out early on Tuesday morning but is now extinguished.
