Rescuers in Yellowstone National Park are searching for a park employee who has been missing since he failed to return last week from a week-long solo excursion through a remote area of the wilderness.

Austin King, 22, was last heard from on Tuesday, Sept. 17 when he called friends and family from the summit of Eagle Peak, the highest point in the Wyoming park, according to a news bulletin from the National Park Service. King was due to return Friday for his boat pickup near Yellowstone Lake's southeast arm, but never returned, the park service said.

A search and rescue effort began the following Saturday morning involving both aerial reconnaissance and ground operations. King’s camp and personal effects were discovered Saturday evening, leading to a larger operation Sunday involving 20 ground searchers, two helicopters, unmanned air systems and a search dog team, the park service said.

As of Tuesday, King remained missing and park service officials are asking for information from other hikers who may have crossed paths with him.

Hiker summits Eagle Peak before vanishing

King, a concession worker at Yellowstone, was dropped off via boat on Saturday, Sept. 14 at Yellowstone Lake for what was to be a 7-day hike to summit Eagle Peak.

Located six miles from the lake's eastern shores, the remote mountain in Wyoming's Absaroka Range peaks at 11,372 feet, making it the highest point in Yellowstone National Park.

Two days after he began his hike, King spoke to a park ranger at Howell Creek cabin in the backcountry, which was not part of his planned route. At the time, King was planning to camp overnight in the area before climbing Eagle Peak on Tuesday, the park service said. 

When King last made contact with anyone, he had reached the summit of Eagle Peak, where he described fog, rain, sleet, hail and windy conditions, according to the park service.

Rescuers from Yellowstone are concentrating their search efforts around Eagle Peak, including the 7.2-mile trailhead. Search teams from Grand Teton national parks and elsewhere also widened the search to areas such as the Shoshone National Forest. 

National Park Service circulates photos of King

The park service is circulating a missing person flier for King, which includes identifying information and two photos of the hiker, including one from the day he was dropped off for the excursion.

According to the flier, King is about six feet tall, weighing 160 pounds. He has brown hair, hazel eyes and was thought to be wearing glasses, a black sweatshirt and gray pants when he vanished.

The park service said that anyone who has traveled around Eagle Peak since Sept. 14 may have crossed paths with King.

Anyone with information regarding his whereabouts can call the Yellowstone Interagency Communications Center at 307-344-2643.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]