A teenage boy visiting Yellowstone National Park was seriously burned when his foot broke through the ground near a geyser by the infamous Old Faithful, officials said.

It was the first known thermal injury in the park this year. Officials urged visitors to stay on designated boardwalks and trails in thermal areas.

The incident occurred on Monday morning when the boy was on a hike in the thermal area of the park in the vicinity of the Lone Star Geyser near Old Faithful when his foot broke through the thin crust and he suffered significant thermal burns to his foot and ankle, according to a statement from the National Park Service.