(CNN) A 48-year-old man suffered severe burns after falling into a hot spring at Yellowstone National Park in Wyoming late Sunday night, the National Park Service announced.

Cade Edmond Siemers told park rangers that he took a walk off the boardwalk without a flashlight and tripped into the thermal water near the cone of Old Faithful Geyser, the NPS said in a statement. The park warns on its website that visitors are to always walk on the boardwalks.

"The ground in hydrothermal areas is fragile and thin, and there is scalding water just below the surface," the statement said.

Siemers was able to walk back to the Old Faithful Inn , where he was staying near the geyser, and call for help around midnight.

Park rangers thought there were signs he had been drinking, according to the statement. They later found a beer can near the geyser, along with one of Siemers' shoes, and footprints leading to and from the geyser.

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