PICKERING, Ont. -- Three teens are facing charges after a stabbing incident at a school east of Toronto left a female staff member and two other teens with injuries.

Police say officers arrived at the Pickering, Ont., school last Wednesday and found a 16-year-old girl suffering stab wounds near the front entrance and an injured female staff member who tried to intervene.

Durham regional police said the girl's injuries were non-life threatening, while the staff member's were minor.

A 16-year-old girl -- who is a student at the school -- was charged last week with weapons dangerous, assault with a weapon, aggravated assault and carrying a concealed weapon.

After reviewing the evidence, investigators said Monday they have also charged a 16-year-old male student and a 17-year-old girl, both from Pickering, with assault.

Investigators say they were involved in an argument before the violence broke out at the school.