Fighting among large numbers of young people erupted Thursday night at Roseville High School, moved to one fast-food restaurant and then another before many officers broke up the mayhem, police and the principal said Friday.

Three people were cut but not seriously injured by what Deputy Police Chief Joe Adams called a "sharp object," and a Chick-fil-A restaurant was damaged extensively. Roseville police and officers from five other law enforcement agencies were needed to restore order, Adams said.

The fighting began at the high school, where an event was being held that welcomed attendees from beyond Roseville, Adams said.

Principal Jen Wilson said the fighting occurred in the parking lot outside the high school, where a "student-sponsored cultural event ... drew a large crowd of non-RAHS youth and young adults. At the conclusion of the event, the large crowd gathered in the parking lot and refused to leave school grounds."

Shortly before 8 p.m., juveniles not associated with the just-concluded event arrived and were the "true agitators," Adams said.

The school resource officer noticed that a couple of the intruders were wearing masks, so "he knew something was about to happen" and called for additional Roseville officers, who were joined by neighboring law enforcement agencies, the deputy chief said.

A number of fights popped up outside the school and continued until officers broke them up, Adams said.

Combatants then moved a little more than a mile away to the Chick-fil-A and resumed fighting, according to the deputy chief, who estimated that the gathering swelled to roughly 200 people.

Adams said one person was cut on an arm or hand and went into the Chick-fil-A, prompting people to barge in and break windows in the process. It took a half-hour for law enforcement to calm the scene, he said.

Undaunted, about 50 people took up the fighting at Raising Cane's. Adams said there were unsubstantiated reports of gunfire. Officers eventually cleared the scene there as well.

Two of the three people who were cut sought medical attention at a nearby hospital, Adams said. None of the injuries were life-threatening.

No arrests have been made but police continue to investigate what happened and who was responsible, Adams said.

Despite the troubling behavior outside the high school, Principal Wilson said, "We continue to be confident in our safety and security systems."