YELLOWSTONE NATIONAL PARK, Wyoming (AP) — Two men face criminal charges for walking onto Old Faithful Geyser in Yellowstone National Park.

Kimberly Guilliams tells KTMF-TV in Missoula, Montana, she saw the men leaning directly over the geyser to take photos earlier this month.

Going off boardwalks in Yellowstone's thermal areas is dangerous and illegal. Old Faithful erupts with boiling hot water about once every hour.

Park officials say the men have been summoned to appear in federal court. They haven't identified the two men.

Several people have been cited over the years for wandering onto Yellowstone's most famous geyser. Several others have been seriously burned by falling or stepping into the park's thermal features.