Two people, a man and a woman, are reported to have suffered burns.
The man had to be taken to hospital by ambulance helicopter after being evacuated from the balcony. The woman was reportedly able to leave the apartment on her own.
Five more people, including a child, were taken to hospital for smoke inhalation.
There must have been a lot of smoke, says Mats Eriksson, press spokesperson for the Stockholm Police.
The police classification of the crime is gross negligence causing public danger and causing bodily harm.
