The girls were likely attacked on their way to school, police told SAnews.gov.za.
"We appeal to members of the public who might have seen or witnessed the death of the girls to assist the police with their investigations," police spokesperson Neville Malila said.
The girls, ages 15 and 16, were found in their school uniforms, and they had cuts on their hands and necks.
Razors, candles and their school bags were found next to them, SAnews.gov.za reported.
No arrests have been made.