Five suspects were in custody early Wednesday in northern California in the gang rape, robbery and beating of a 15-year-old girl outside her high school homecoming dance, KTVU.com reported.

Authorities in Richmond, Calif., said they arrested two adults and three juveniles and were searching for others believed to be involved in the alcohol-fueled attack Saturday night in a secluded courtyard on the grounds of Richmond High School.

Evidence suggests there may have been up to 10 assailants, Richmond Police Lt. Mark Gagan told KTVU.com, and the assault was likely witnessed by as many as a dozen people — some of whom laughed and snapped photos of the rape on cell phone cameras but did nothing to stop it.

"She was raped, beaten, robbed and dehumanized by several suspects who were obviously OK enough with it to behave that way in each other's presence," Gagan said earlier this week. "What makes it even more disturbing is the presence of others. People came by, saw what was happening and failed to report it."

More coverage at KTVU.com.

The Tuesday night arrests include a teenager from San Pablo; a 21-year-old Richmond man identified as Salvadore Rodriguez and a teenager from Pinole who surrendered to police after they went to his home with a warrant earlier in the day, KTVU.com said. The juvenile suspects are boys ages 16 and 17, police said.

Two others were arrested Monday: 19-year-old Richmond High School dropout Manuel Ortega, who was booked on $800,000 bail, and a 15-year-old male freshman.

The victim, who police say has been helping in the investigation, left the high school homecoming dance about 9:30 p.m. Saturday and was heading to meet her father for a ride home when a classmate invited her to join a group drinking in the courtyard.

Shortly afterward, the girl was allegedly robbed, beaten and gang-raped for more than two hours before police intervened.

Investigators believe the attack not only was carried out by as many as 10 people aged 15 to mid-20s but also was watched by up to 12 others and may have been videotaped and photographed with cell phone cameras, according to KTVU.com.

The victim had consumed a large amount of alcohol by the time the assault began, police said. When officers arrived at the scene, they found the girl semi-conscious near a picnic table. She is hospitalized with non-life-threatening injuries.

Authorities stepped up their investigation Tuesday night, sending a SWAT team out with arrest warrants. More arrests are coming, Gagan said.

"That list will increase, I expect, as we get people in custody, as they tell us what other people did and what they saw," he told KTVU.com.

The victim had been verbally abused by her classmates in the past, a student told the station.

“They used to make fun of her because she had a crush on a boy in class,” said Richmond High senior Susan Meas. “And they used to make fun of her because of the jeans she wore and stuff. She had to barge out of class crying one day."

The Associated Press contributed to this report.