HAWTHORNE (AP) — Officials at Los Angeles County’s Hawthorne High School beefed up security Thursday following a nearly hourlong brawl between students that forced police to restore order and ended in three arrests.

Officers planned to interview students as they investigate the melee involving multiple students that erupted Tuesday. The school, with about 2,000 students, was closed for the Veterans Day holiday Wednesday.

Cellphone cameras recorded crowds of kids surrounding several groups fighting. One video showed two girls scrapping, and in another, a boy hurled a rubber trash can. School officials called police.

Investigators were still looking into what sparked the fights, Lt. Aimee Yoshida said.

Three students were arrested on suspicion of assaulting an officer and a school employee, Yoshida said. Their names were not released. One student was treated at the scene for minor injuries.

Sophomore Samuel Lyman-Cruz said he didn’t know any of the students involved but heard that the fight began by freshmen trying to prove themselves.

“Sometimes freshmen like to start problems with juniors and seniors,” Cruz told The Associated Press as he got ready for school early Thursday.

The 15-year-old wasn’t nervous about going back and said he didn’t think there would be more fights.

School leaders sought to reassure parents at a meeting Wednesday night. The school’s principal, Mark Newell, said officials would go classroom to classroom to make sure students felt safe.

“Our goal is to keep children here safe. And they’re going to be,” Newell told reporters Wednesday night.

Hawthorne High is one of seven schools in the Centinela Valley Union High School District in southwestern LA County.