SEATTLE -- Sheriff's office investigators are asking for the public's help in identifying a woman they believe was a victim of Green River Killer Gary Ridgway.

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Deputies said a vertebrae was found last month at a site where Ridgway said he dumped one of his victims. The Green River Task Force searched the area several times in 2003 and found human bones. A new search on July 6 used a Transportation Department tanker truck to wash and sift through soil near Kent, off the Kent-Des Moines Road, just east of Military Road South.

Video: Ridgway Makes Confession About Early Victim
Video: Ridgway Interrogation, Confession

The King County Medical Examiner's Office said the victim was a white female likely killed in the 1970s.

Ridgway described his victim as Caucasian with long hair.

Sheriff's detectives asked that anyone who knew a female matching this description and who disappeared in the 1970s to call them at (206) 296-7575.

Ridgway is serving 48 life sentences for killing 48 women.