Two teenage boys have been arrested in connection with the alleged sexual assault of at least one of three girls who passed out at a San Fernado Valley park, police said.

A 16-year-old boy and a 15-year-old boy were arrested Friday after police interviewed several students believed to be at Mason Park in Chatsworth around the time the high school freshmen girls were there on Thursday. The older teen was booked on suspicion of sexual battery and the younger boy was booked on suspicion of sexual assault on a victim incapable of defending herself, Detective Mike Fesperman said.

Investigators believe the girls — one found unconscious in the men's bathroom, and the others near picnic tables — were drugged, but they also may have been drinking.

The girls were treated at a hospital and released. They are cooperating with detectives but don't remember what happened while unconscious, Capt. Steve Ruiz said.

Police are doing tests to determine if the girls were given a "date rape" drug or had drunk alcohol.

People playing basketball at the park Thursday morning became concerned about the girls who appeared to be unconscious.

Some witnesses said they saw the girls drinking alcohol and smoking something, Detective Shannon Smith said.

About 50 teenagers were hanging out in the park earlier that morning, she said. Most left by the time of the incident and the rest fled when police arrived.

Police also found backpacks, a bag of candy and soda bottles at the scene, Ruiz said.

Classes at Chatsworth High School, near the park, started later than usual this week because of standardized testing. However, buses kept their regular schedules so students who were not taking the state tests had to wait for classes to start.

One Chatsworth student, Sarah Dibble, told KCBS-TV that her classmates often play hooky on testing days. Not all students are tested, and during down time many are "just sitting there doing nothing," said Dibble.

"It's basically go to school, watch a movie, do nothing. So it's basically not worth going to school," she said.