RICHMOND — As police interrogated a sixth person arrested on suspicion of raping a 15-year-old Richmond High School student outside a homecoming dance, prosecutors declined Friday to file criminal charges against a 21-year-old man previously arrested.

Salvador Rodriguez, of Richmond, was scheduled to be released Friday from County Jail, in Martinez, after the Contra Costa County District Attorney's Office announced there was insufficient evidence to prosecute him for the Oct. 24 assault.

"There does not appear to be sufficient evidence at this time," Richmond police Lt. Mark Gagan said. "However, the investigation is ongoing, and the forensic evidence is still being examined."

Four other suspects

— Cody Ray Smith, 15; Ari Morales, 16; Marcelles Peter, 17; and Manuel Ortega, 19 — were arraigned Thursday on charges that call for life prison sentences. They are jailed without bail. Prosecutors cited the brutality of the crime as reason for charging the underage suspects as adults.

Police on Thursday night arrested Jose Carlos Montano, 18, near his San Pablo home in the 1800 block of 16th Street.

Gagan said Montano played a "significant" role in the assault and police will request felony charges of rape, rape in concert with violence, penetration with a foreign object and a special enhancement requesting life in prison.

"The charges accurately reflect the severity of (Montano's) actions," Gagan said.

Dara

Cashman, head of the District Attorney's Family Violence Prevention Unit, said she will meet with detectives late Monday to consider charges against Montano.

Montano is being held in County Jail in lieu of $1.3 million bail. Meanwhile, police continue to search for additional suspects.

Staff writer Karl Fischer contributed to this story.