A search is underway in Yosemite National Park for a backpacker who disappeared over the weekend while hiking with a group, officials said.

Hayden Klemenok, 24, was with his group at Upper Chilnualna Falls when he stopped at the Chilnualna Creek near the trail junction around 2 p.m. Sunday and was swept away, park officials said.

Klemenok has yet to be found after entering the water, the park said.

The 24-year-old was taking an annual hiking trip with college friends, his father Kevin Klemenok told KNSD-TV. Witnesses told the station that Klemenok got down on his hands and knees next to the turbulent river to take a drink or cool off when the rushing waters swept him away.

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The park released a photo of Klemenok wearing the clothing that he disappeared in a tan, brimmed hat, white sunglasses, red T-shirt, blue swimming trunks and white Adidas shoes.

Klemenok is a graduate of San Diego State University and lived in the Bay Area, where he worked as a financial analyst, his father said.

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The Chilnaulna Falls Trail is eight miles long with a 2,400-foot elevation gain, according to the park’s website. The site describes the route as "strenuous" with views of the falls and Wawona Dome.

Officials asked anyone who was hiking in the area at the time Klemenok disappeared to contact the park at YOSE_Desk_Officer@nps.gov or 209-379-1992.

"Simply knowing where you went and when you were there may help us focus the search, whether you saw anyone or not," park officials said.