Autopsy reports show three sisters found dead in their beds in River Falls suffered neck injuries.
Prosecutors charged the girl's father, 34-year-old Aaron Schaffhausen of Minot, N.D., with three counts of first-degree intentional homicide Thursday. A judge set his bail at $2 million.
According to a criminal complaint, Schaffhausen called the girls' mother Tuesday and told them he had killed the children. He later turned himself in to police.
Police found 11-year-old Amara Schaffhausen, 8-year-old Sophie Schaffhausen and 5-year-old Cecilia Schaffhausen tucked into their beds, blankets up to their necks. Their faces were covered with what appeared to be dried blood.
Autopsy reports cited in the complaint said all three died of what the reports termed "sharp force injury" to the neck. Cecilia also had been strangled.
The girls were found in the house they shared with their mother in River Falls on Tuesday. The Schaffhausens divorced last year.
River Falls Police Chief Roger Leque said there's no danger to the rest of the community. It's located about 30 miles east of Minneapolis-St. Paul.