It was shortly after 12 o'clock on Sunday that the police were alerted to an address in Västerås where a 45-year-old man was found dead.
The place was cordoned off and questioning was carried out.
A man was arrested and later arrested on suspicion of murder.
Chamber prosecutor Jessica Wenna is leading the investigation against the man, but at the moment cannot say more than that he is suspected of murder as the investigation is in a sensitive situation.