RICHMOND -- Contra Costa officials were awaiting the extradiction Thursday of a Richmond woman who has been arrested for an illegal relationship with a 15-year-old boy from El Sobrante, for supplying the boy with illicit substances and for concealing him from his parents.

Detective Sgt. Mitch Peixoto said Genevieve Elise Silva, 20, of Richmond, was arrested Wednesday in Oklahoma where her mother lived. An extradition hearing was scheduled for Thursday.

Silva is accused of providing ecstasy and methamphetamine to a 15-year-old De Anza High School student during sexual encounters and convincing the boy to move to Oklahoma with her over the summer, Peixoto said.

The boy is now receiving treatment for drug addiction. He began to tell his family and investigators what happened once treatment began, Peixoto said.

Family members contacted police about the case because they were concerned that Silva might try to engage in similar illegal behavior with other young boys.

Peixoto said the victim met Silva through her younger brother in June. Both boys attend De Anza High School in Richmond.

The victim ran away from his home and moved in with Silva, her brother and her father. The boy's family immediately reported him as a runaway, Peixoto said.

Investigators are not sure how long the victim lived in Richmond but know that he started a sexual relationship with Silva while living with her. He said that while living with her, she supplied him with amphetamines, ecstasy and marijuana.

At some point -- Peixoto said investigators are not sure exactly when --Silva and her mother, Rhonda Silva, who is estranged from her husband, took the victim to Roosevelt, Okla., where the sexual relationship and drug use continued.

Investigators are still not sure of Rhonda Silva's exact role in the case.

The victim's parents found out where he was by talking to school friends and De Anza school authorities, Peixoto said. When police in Roosevelt picked up the victim he was reportedly under the influence of drugs.

Peixoto said he believes the victim is in rehabilitation out of state.

The boy had reportedly told his family the addresses of pornographic Web sites where Silva appeared.

Peixoto said he found Silva's images on several pornographic Web sites. Police haven't been able to confirm or deny that Silva has been involved in pornography with young boys. The Web sites Silva appeared on do not appear to be involved in underage pornography, Peixoto said.