Durham police have added two new charges against the 14-year-old teenage girl accused of injuring several people with knives during an attack last month at a Pickering, Ont., high school.

The girl, who cannot be named because of the Youth Criminal Justice Act, is now being charged with two counts of assault with a weapon. The charges were added at a bail hearing she attended on Tuesday, police said in a release.

Police told CBC News they reviewed security camera footage taken inside the school and found the accused swung at two students inside the school. Police said no contact was made but the act still warrants the charge being laid.

In February, the teen was facing 15 charges including one count of assault, six counts of assault causing bodily harm, seven counts of assault with a weapon and one count of possession of a weapon for a dangerous purpose. 

It is alleged that on Feb. 23, 2016, a female student went to Dunbarton High School with two knives and started attacking both students and staff. Police said nine people, including three teachers, were stabbed in the attack. Four people were taken to hospital, including one with serious injuries. 

Police have not yet provided a possible motive for the attack but it did not appear that any of the victims were targeted. 

With files from The Canadian Press