A human skull found at a dump site in the southwest corner of Washington County earlier this month is at least four centuries old.
Washington County Undersheriff Steve Johnson says the state Medical Examiner's Office has determined the skull is over 400 years old.
The skull was found on private land just off Highway 11 north of Skiatook on May 6, 2014.
Johnson says the ME's office is now trying to identify which Native American tribe it belongs to so the skull can be returned to that tribe.
Johnson says a search of the site by deputies and the Oklahoma State Bureau of Investigation failed to turn up any other human bones. He says it is unknown if the skull belonged to a male or female.