Rescuers in Yellowstone National Park are searching for Austin King, 22, a park concession worker who went missing after failing to check in following a weeklong trek around Eagle Peak.

King was last heard from on Sept. 16 after he reached Eagle Peak’s summit, where he described difficult weather conditions.

He was supposed to be picked up by boat on Sept. 20 at Yellowstone Lake, but never arrived.

Search efforts, which began on Saturday, include over 20 ground searchers, helicopters, drones, and a canine team, NBC News has reported.

King’s personal belongings were found at an encampment, but he remains missing.

Written by B.C. Begley