A 16-year-old American girl died when she stumbled and plunged more than 300 feet down an embankment on a sightseeing walk in Switzerland, authorities said Monday.

First responders who rushed to save her found the girl’s lifeless body in the environs of the Trient River below a popular walking path, police in the country’s Valais district said in a statement.

The teenager, who was not publicly identified, was with her best friend and the friend’s family when she fell Sunday morning, police said. The friend’s father got stuck on a rock wall as he went to help the girl who stumbled, they said.

He was rescued and was uninjured, Valais police said. The emergency response included two helicopter crews, two regional rescue teams and emergency psychologists, police said.

No other injuries were reported.

The U.S. Embassy in Switzerland and Liechtenstein did not immediately respond to a request for information.

The local prosecutor’s office has opened an investigation into what caused the girl to stumble in conjunction with Valais police, the police statement said.

The fall happened in the area of Gorges Mystérieuses à Tête Noire — the Mysterious Gorges of Tête-Noire — shortly after 10:30 a.m., police said.

The destination, popular with international hikers, is near the border with France about 90 miles northwest of the Matterhorn alpine peak by road.

The Swiss government’s tourism agency said the circa-1884 Tête-Noire pathway, including stone steps and footbridges, descends about three-quarters of a mile to the bottom of a gorge.

The walk includes views of “idyllic waterfalls” and the Grotte aux Nymphes, described by the agency as “an authentic natural cathedral hidden under gigantic slabs of rock that lean one against the other.”

It is not described as particularly dangerous, with the tourism agency saying it is suitable for visitors as young as 6, though it is not accessible via wheelchair or for those with physical challenges and disabilities.

Spring in Valais has been perilous. In April, three skiers, including a 15-year-old American boy, were killed in an avalanche on the slopes of Riffelberg near the Matterhorn, police said.

This article was originally published on NBCNews.com