YELLOWSTONE NATIONAL PARK, Wyo. (AP) _ Three young park concession employees on a late-evening outing plunged into a 178-degree hot spring. One died and two were in critical condition Wednesday.

The three were burned late Monday in the Cavern Spring, a 10-foot-deep pool in the Lower Geyser Basin, seven miles north of Old Faithful in the middle of Yellowstone National Park.

``These three teen-agers jumped into the pool thinking it was cold water and were amazed to find it was not,'' Dr. Jeff Saffle, treating the survivors at a Salt Lake City hospital, said Wednesday.

But late Wednesday, park spokeswoman Cheryl Matthews said the two survivors told first-aid workers that they fell in trying to jump over what they thought was a small creek after returning from a swim in the Firehole River.

Yellowstone's thermal pools are often surrounded by thin, fragile crusts. Numerous warning signs are posted. Visitors to the Lower Geyser Basin are urged to stay on a half-mile boardwalk over the treacherous terrain.

``I would not venture off this boardwalk. You couldn't pay me enough to set foot off this,'' said Carla Wilson, a visitor from Denver.

Sara Hulphers, 20, of Oroville, Wash., was burned over her entire body and died a few hours later at the University of Utah's Intermountain Burn and Trauma Center in Salt Lake City.

Tyler Montague, 18, of Salt Lake City and Lance Buchi, 18, of Sandy, Utah, were in critical condition.

Saffle said Montague and Buchi were in shock and barely coherent after being rescued but told doctors that they dove into the pool on purpose. He estimated their changes of survival at 30 percent to 40 percent.

``It is way too early for us to be optimistic,'' Saffle said.

Rangers don't think alcohol was a factor, park officials said. Matthews said such accidents are infrequent. In 1998, a man fell into a thermal pool and suffered second-degree burns.

In Oroville, in north-central Washington, high school teacher George Thornton remembered Hulphers as ``very outgoing, friendly, very accepting of others.''

``She's one of the good kids, really neat, just a treasure of a kid,'' he said, his voice choking. ``You work very hard as a teacher, and every once in a while you get a great kid, one you know will be a great person and a great parent. This is just tragic. She was a great person.''

The three teens worked in the Old Faithful area, Hulphers and Buchi in the Old Faithful Inn and Montague at the Old Faithful Lodge.

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