The search for Allyson Watterson will change on Friday.
Watterson has been missing since Sunday when her boyfriend, Benjamin Garland, says they became separated during a hike in a rural, wooded area.
The Washington County Sheriff's Office says starting Friday the search will be looking for specific evidence in the disappearance. They wouldn't discuss what new clues caused them to change the type of search.
On Thursday, an Oregon Army National Guard helicopter assisted with the search along with drones, a K-9 and around 100 searchers.
Garland made his first court appearance on unrelated charges.
Investigators say Garland has been cooperative in the search for Watterson.