RICHMOND (BCN) -- The Contra Costa County District Attorney's Office has charged  four of five people arrested in connection the two-and-a-half-hour gang rape  of a 15-year-old girl during Richmond High School's homecoming dance Saturday  night.

Deputy District Attorney Dara Cashman said she filed charges Wednesday  afternoon against 19-year-old Manuel Ortega and three juveniles who will be  charged as adults. She has not yet released their names.

Charges have not been filed against the fifth person who was  arrested, 21-year-old Richmond resident Salvador Rodriguez.

Ortega, who was arrested shortly after the assault as he allegedly  ran from the area, is being charged with robbery, assault by force likely to  produce great bodily injury, and rape in concert, Cashman said.

A 15-year-old San Pablo boy who was pulled out of class and  arrested on Monday is being charged with rape by foreign object in concert,  as are a 16-year-old San Pablo boy and a 17-year-old Pinole boy who were  arrested Tuesday night, Cashman said.

The 16-year-old has also been charged with robbery.

All four also face special allegations that make them eligible for  life in prison if convicted, Cashman said.

They will appear in Contra Costa County Superior Court in Richmond  on Thursday morning.

Detectives are continuing to interview witnesses and now believe  that between seven and 10 people were involved in robbing, beating and  sexually assaulting the victim, a Richmond High School student, in front of  as many as a dozen onlookers.

Police received a call reporting the incident at about 11:50 p.m.,  police Lt. Mark Gagan said. He said investigators believe the attack began  around 9:30 p.m. and lasted nearly two and a half hours.

The victim left the dance, intending to get a ride from her  father, police said. Instead, a classmate beckoned her to a secluded corner  on the north side of campus, where a group of people had gathered to drink,  Gagan said.

After drinking a large quantity of alcohol, the victim became  inebriated and members of the group began assaulting her, police said. When  police arrived and broke up the activity, the victim was airlifted to a  hospital and is in stable condition.

Four Richmond police officers and several school administration  members were providing security at the dance, but didn't know the attack was  going on, West Contra Costa Unified School District spokesman Marin Trujillo  said.

Richmond police are offering a $20,000 reward for information  leading to the arrest and conviction of anyone involved in the attack, Gagan  said.

The school board has relocated a safety subcommittee meeting  scheduled for tonight to Richmond High School. The meeting is being held in  the high school's library and will include discussions on campus safety and  safety measures for events during non-school hours, Trujillo said.

Richmond High School has also organized a meeting for parents  Saturday at 10 a.m. in the school gym to discuss the attack and address  concerns.

The school board is also seeking bids for plans to install digital  security cameras on campus, and build a fence around the perimeter, Trujillo  said. While initial plans did not include a camera in the alleyway where the  attack took place, "I'm pretty sure they are going to be looking at that area  now," Trujillo said.
           
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