The police suspect the man with probable cause, the higher degree of suspicion, reports Swedish Radio News.
Homes in the centre of Umeå were evacuated as the wooden building with six apartments burned to the ground.
The alarm was raised over the fire at Smedsgatan street at 3am.
Firefighters brought the fire under control early on Saturday morning. People living near the destroyed building were able to return home.
One person has been taken to hospital suffering from smoke inhalation.
No one is thought to have been trapped in the burning building says fire leader Conny Qwarforth to news agency TT.