Cpl. John MacDonald from the Maine Warden Service said an "intensified search strategy" was being put into place for the weekend search for Geraldine Largay of Brentwood, Tenn.
She texted her husband July 22 but failed to meet up with him in Wyman Township.
The original search area covered more than 80 square miles. But searchers later narrowed the focus to a 14-mile stretch of trail.
Largay's husband, George, has been providing supplies and support for his wife's hike from Harpers Ferry, W.Va., to Maine's Baxter State Park. He said she contacted him on July 21 from atop Saddleback Mountain and texted him again the following morning before disappearing.