The police were alerted early Saturday morning that a person had been found dead in Avesta in Dalarna County.
"The circumstances at the scene led to a preliminary investigation into murder being initiated," the police write on their website.
According to Aftonbladet, both a residence and a forest area were cordoned off.
"Continued investigative measures are underway intensively with technical examinations, interrogations and other measures," the police write.
The suspect was arrested on probable cause - the higher level of suspicion - last Saturday.
