A hydrothermal explosion sent a towering column of boiling water, mud and rock shooting into the air at Yellowstone National Park in Wyoming on Tuesday morning, destroying a section of boardwalk and sending dozens of tourists running for safety, officials said. No injuries were reported, according to the United States Geological Survey, but the area remained closed to the public.

The explosion occurred around 10 a.m. in the Biscuit Basin area of the park. Several tourists captured video of the event, and in some footage an adult can be heard shouting at children to run.

Vlada March, a tourist who recorded the event on her cellphone, said she was taking a guided tour with her family when the guide pointed out steam rising from the ground.

“‘Oh look,’ he said. ‘This is unusual.’ I took out my phone like everyone does. Suddenly it became a huge, dark cloud full of rocks,” she said in a phone interview. “It was a huge cloud, it covered the sun. For a few moments, you couldn’t see the sun it was so dark.”

Ms. March, of Palm Desert, Cal., said she shouted for her two young sons to run, and looked frantically for her 70-year-old mother, whom she had lost sight of. When her mother reappeared, Ms. March said, “she was covered in ash, head to toe.”

The explosion was a couple of miles north of the Old Faithful Geyser, which regularly shoots steam into the sky. “This is quite a bit different than Old Faithful,” said Michael Poland, the scientist in charge at the Yellowstone Volcano Observatory, who said the hydrothermal event took place near Black Diamond Pool in Biscuit Basin.