The Los Angeles Police Department says it is investigating 14 teenagers in connection with a series of sexual assaults against two high school students.

The sexual assaults have allegedly been happening on a regular basis since late 2013 at Venice High School, according to Los Angeles Police Cmdr. Andrew Smith as quoted in a Fox News report.

Eight of the suspects were arrested on Friday morning on school grounds, and a ninth was taken into custody after being found off campus. A 10th surrendered that afternoon, and police were searching for the remaining four.

Los Angeles Unified Interim Superintendent Ramon Cortines called it a “painful moment” for the school and the district, and said that crisis counselors would be made available for students, according to the report.

Some of the incidents were forcible, but some were not — however, the victims were too young to give consent, according to Smith, who called it a “terribly tragedy,” and pleaded with other victims to come forward.

A former head of the schools parent-teacher-student association (PTSA) said she had no idea anything was going on at the school before the arrests.

Linda Patterson Salib, the former PTSA head, said that she had been a part of the school for a long time and hadn’t even “heard anything whispered,” further adding that the incident came as “quite a surprise,” according to the report.

Venice High School is located in Northwest Los Angeles near Santa Monica. It is the alma mater of some notable alumni, including actor Beau Bridges, Washington Nationals pitcher Doug Slaten, and In-N-Out Burger founder Harry Snyder.