The rescue service was alerted to the apartment building in Hammarkullen shortly after 18:00.
Around 30 firefighters worked on the scene and nine ambulances were on site to care for any injured people.
Residents in the house were evacuated due to the fire smoke.
The fire started in the stairwell and the rescue service therefore had to evacuate residents through windows.
They have been taken to a collection point and according to the rescue service, it is unclear whether they will be able to return to their homes later tonight.
Three people have been taken by ambulance to hospital, the police tell TT.
26 people have received care on site, five of them are children who have received care from ambulance personnel.
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According to police spokesman Morten Gunneng, it was a murder fire.
- It is obvious that it is laid out, he says.
The police have cordoned off the place and are hearing people who may have valuable information about the process.
The rescue service has related the fire and now it remains to ventilate the homes on fire smoke and do a damage check.
The police investigation is continuing and a technical investigation will be carried out.