“We have cordoned off the area and police forensics were swiftly on the scene,” said Stockholm police spokesman Lars Byström to the Metro daily.
According to police, the house was completely in flames when emergency services arrived. The two people were found dead when fire fighters searched the house after the flames were successfully extinguished.
The identity of the deceased or exactly how the fire started remained uncertain on Sunday morning, but circumstances indicate arson, according to the police.
A preliminary investigation has been opened into suspected aggravated arson or double murder.
According to Södertörn fire services a third person managed to get out of the house after the fire started and called the police and fire services.
Dalarö lies in Haninge municipality in southern Stockholm and is a popular summer holiday destination for Stockholm residents with a large number of wooden holiday homes on the 168 hectare island.