Classes were proceeding normally amid heightened security Thursday at a Los Angeles-area high school where eight students were injured in a courtyard brawl.

Ten additional school police cars were patrolling the campus of Carson High School, but no further incidents have occurred, said Monica Carazo, spokeswoman for the Los Angeles Unified School District.

First period attendance was lower than normal at 83 percent. It's usually 90-plus percent, Carazo said.

The stepped up security comes after a melee involving about 30 students erupted Wednesday during the school's midmorning snack break. Four students were taken to hospitals and four were treated by the school nurse. Seven students were arrested or suspended for fighting.

Carazo said she did not have an update on the conditions of the injured students.

The cause of the fight is still under investigation by the school police, although initial reports that it was racially motivated were not substantiated, said Principal Windy Warren, principal of the 3,000-student school, located south of downtown Los Angeles.

Warren said student leaders reported no tensions among the ethnically diverse student body.

"This is a very unusual incident for the Carson campus, which has been very peaceful this entire school year," she said.