BERKELEY (CBS SF) — Berkeley High School administrators ramped up security on campus Monday, following a huge brawl that broke out after school involving hundreds of students, non-students and adult spectators last Friday. About two dozen police were called in to disperse 15-20 street fights that erupted in the span of about 40 minutes.

The fights broke out around 3:40 p.m. on the east side of campus near Shattuck Avenue. In a short time a crowd estimated from 400 to 500 people had gathered, jumping on cars, blocking BART station entrances and filming the fights.

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According to Berkeleyside, members of the crowd were arguing with each other, “calling each other out,” setting trashcans on fire, and lighting fire crackers.

Authorities said some of the students involved were from Berkeley High, but a number came from neighboring schools in San Leandro and Oakland.

Police arrested 3 Berkeley High School students and 2 Berkeley Technology Academy students. The students also face discipline by the school. Administrators are trying to identify other students who were involved using cellphone video and other sources.

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Berkeley High School’s interim principal, Kristin Glenchur said she first contacted police after hearing that fights broke out Friday during lunch, on Shattuck Avenue. Administrators got word that out-of-town students planned to fight Berkeley High students. The campus remained open, but non-students were not allowed on the grounds.

In an email to the BHS community, the principal said school would remain open this week, with heightened security. She asked parents and guardians to advise their students to “move away from gathering crowds” to avoid risk of injury, and not impede the work of security staff.

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“We are going to make sure we have extra support here,” Glenchur said.