An autopsy confirmed a 30-year-old Jackson woman who died in Yellowstone National Park’s Bechler River drowned, park officials said Monday.

Heidi Llewellyn Smith died Thursday after she told her three friends she wasn’t feeling well and was going swimming.

It remains unclear whether illness played a role in the drowning. National Park Service special agents are investigating the incident, Yellowstone spokesman Al Nash said.

A friend found Smith in 4 feet of water against a log near the Bechler Ford campsite about 5.5 miles from the Bechler Ranger Station.

She was not breathing and did not have a pulse. The friend ran to the Bechler Ranger Station and reported the incident at 1:45 p.m.

Rangers and a medic responded on horseback and in a National Park Service helicopter from Mammoth Hot Springs. Smith was declared dead at the scene.

It was the first accidental death in Yellowstone this year.

In June, a 20-year-old Utah man climbed into the Yellowstone River at the Brink of the Lower Falls overlook and let the current carry him over the 308-foot waterfall.

The Bechler region of Yellowstone National Park is in the southwest corner of the park and is only accessible from Ashton, Idaho, or Grassy Lake Road in Grand Teton National Park.