Investigators believe the young sisters were the victims of a violent crime. Their mother came home just before 5 am and discovered their bodies in the family's apartment in Krailling, on the southwest outskirts of Munich.
A police spokesman said officers were carrying out a “double homicide” investigation. He declined to comment on news reports that one of the girls had been alive when the mother returned home.
The girls' bodies were found separately in their respective bedrooms.
Daily Süddeutsche Zeitung reported that the woman was separated from the girls' father and worked as a waitress in a pub. Neighbours said the woman's partner - who was with her when she arrived home - was the landlord of the pub. They said that although the women was separated from the girls' father, he still saw his daughters regularly.
Investigators had sealed off the area around the second-floor apartment and were gathering evidence and interviewing potential witnesses Thursday morning. About 35 officers were involved in the investigation. A helicopter was also being used to search the surrounding area.
However, the circumstances of the girls' deaths remain unclear.