A young woman who had summited Middle Teton in Grand Teton National Park somehow became separated from her partner on the way down and fell an estimated 80 feet to her death, according to park officials.

Rangers are investigating the accident that killed Jillian Drow, 21, of Chelsea, Michigan.

According to a park release, the woman and a partner were part of an eight-person University of Michigan group in the park. The two summited 12,804-foot Middle Teton on Tuesday evening but became separated on the way down. When Ms. Drow failed to return to a backcountry camp in Garnet Canyon, the group’s leader began to search for her. He discovered the woman, who was unresponsive and lifeless, at approximately 9 p.m., the release said.

Teton Interagency Dispatch Center received a cell phone call from the University of Michigan group leader at 7:30 p.m. Tuesday. He reported that a member of their party was missing and they were searching for her. A second cell phone call was received at 9:03 p.m. reporting the woman's body had been found, the park release said.

Because of the late hour and waning light, a helicopter flight was not possible. However, four park rangers hiked up to the Garnet Canyon campsite to begin a recovery operation; they arrived at 1:30 a.m. on Wednesday. Six of the University of Michigan students hiked out of the canyon to the valley floor in the early hours of Wednesday morning, while park rangers remained with the woman's body and the group leader to make preparations for an aerial evacuation with daylight on Wednesday morning.

A Teton Interagency helicopter flew the body and the group leader out at 9:30 a.m. on Wednesday, just a few hours before a severe lightning storm enveloped the Teton Range, park officials said. The lightning storm injured 17 climbers on the 13,770-foot Grand Teton and a full-scale rescue mission was launched by park rangers to rescue and extricate the injured climbers in the aftermath of the Drow evacuation.

Park rangers will continue their investigation to circumstances surrounding Drow’s death. No further details are available at this time.