A teenage girl and her boyfriend were arrested on suspicion of murder after the bodies of the girl's mother and stepfather were found in different parts of Los Angeles County.

The 16-year-old boy and 15-year-old girl were being held without bail Thursday after the discovery of human remains in shallow graves in the suburban cities of Long Beach and Norwalk, KTLA reported.

The victims vanished from their Compton home last Tuesday "under suspicious circumstances," according to Lt. Mary Leef, of the Los Angeles County Sheriff's Department.

The woman's body was found partly buried Saturday after a passerby noticed a foul smell. Late Wednesday, the suspects gave police information about the location of the man's body, KTLA reported. He was found a short time later in a shallow grave close to the couple's house.

Neighbors told KTLA that the girl was seen discarding some of her mother's belongings in recent days. One neighbor said she asked the girl where her mother was and was told that the woman was in the hospital undergoing surgery.

Friends of the girl suggested that she had been sexually abused. "The only thing she told me was that she got raped," one friend told the station.

It is not known yet how the victims died.