Yellowstone National Park, Wyo. — A New Hampshire woman suffered severe burns on her leg after hiking off-trail in Yellowstone National Park and falling into scalding water in a thermal area near the Old Faithful geyser, park officials said.

The 60-year-old woman from Windsor, New Hampshire, along with her husband and their leashed dog were walking off a designated trail near the Mallard Lake Trailhead on Monday afternoon when she broke through a thin crust over the water and suffered second- and third-degree burns to her lower leg, park officials said. Her husband and the dog weren’t injured.

The woman was flown to Eastern Idaho Regional Medical Center in Idaho Falls, Idaho for treatment.

Park visitors are reminded to stay on boardwalks and trails in hydrothermal areas and exercise extreme caution. The ground in those areas is fragile and thin and there’s scalding water just below the surface, park officials said.

Pets are allowed in limited, developed areas of Yellowstone park but are prohibited on boardwalks, hiking trails, in the backcountry and in thermal areas.

The incident is under investigation. The woman’s name wasn’t made public.

This is the first known thermal injury in Yellowstone in 2024, park officials said in a statement. The park had recorded 3.5 million visitors through August this year.

Hot springs have injured and killed more people in Yellowstone National Park than any other natural feature, the National Park Service said. At least 22 people have died from hot spring-related injuries in and around the 3,471-square-mile national park since 1890, park officials have said.