Six people were taken to hospital following the fire.
The Häme police suspect foul play in the fire in an apartment building in Saimaankatu, Lahti, a week ago.
However, Markku Vornanen, the head of the investigation, cites investigative reasons and does not want to give the name of the offence, the number of suspects or any other details of the case.
Six people were taken to hospital after the early morning fire in an apartment block. A total of 15 people had to be evacuated from the seven-storey building.
The apartment was badly damaged and other apartments in the same building also suffered smoke damage.