The cause of death has not yet been determined and an investigation is continuing, FOX 12 of Oregon reported.
The Washington County Sheriff’s Office said in a statement that it “offers their sincerest condolences to the family as they have faced unthinkable circumstances for the past six months since Allyson was first reported missing.
“We’d also like to thank everyone who helped in the extensive search efforts and to those who provided valuable tips and information to our investigators during this time," the statement continued.
Watterson went missing just before Christmas in North Plains, about 18 miles west of Portland, after reportedly going hiking with her boyfriend, Benjamin Garland.
Garland remained behind bars Friday after pleading guilty to charges unrelated to Watterson’s disappearance, FOX 12 reported.
The remains were found last Saturday by the owner of a North Plains property, in the same area where Watterson’s belongings were found earlier this year, authorities said.