Authorities in Grand Canyon National Park are searching for more than 20 missing people after a flash flood tore through the park, causing significant damage to hiking areas. On August 29, floodwaters pummeled Bright Angel Canyon, a ravine that feeds into the Grand Canyon, and Phantom Ranch, the lodge at the canyon’s base, destroying historic bridges, trails, and structures.

Now, the National Park Service (NPS) is asking for help in finding those missing.

As of the publishing date of this story, 62 people have been evacuated from Phantom Ranch and the lower North Kaibab Trail, a 14-mile hiking route from the canyon’s North Rim. More evacuations are scheduled to take place on of August 30 from Cottonwood Campground and Phantom Ranch, authorities said.

“If you know of hikers or backpackers who were in the Bright Angel Creek corridor on August 29, or if you had a campground reservation in the affected area, please contact the NPS Investigative Services Branch (ISB),” NPS wrote in a statement. People with information about hikers in the following areas should email ISB at nps_isb@nps.gov or call the ISB tip line at 1-888-653-0009:

• Traveling the North Kaibab Trail from the North Kaibab Trailhead to Phantom Ranch
• Staying at Bright Angel Campground or Cottonwood Campground
• Traveling through “the Box” north of Phantom Ranch

“Please provide any information you have, including a person’s name, approximate location, travel plans, group size, clothing or backpack description, or when they were last known to be in the area. You do not have to provide your name,” NPS wrote.

Officials also closed the Colorado River to boaters, citing concerns over metal structures and debris entering the river. NPS says it’s working with rafters and kayakers already on the river. Anyone planning to visit Grand Canyon National Park should reconsider, authorities say.

“Grand Canyon National Park staff, in coordination with the Arizona Department of Public Safety, are continuing evacuation and response efforts and working to account for individuals who may have been in the affected area,” the National Park Service said in a statement sent to Outside. 

“Evacuees are being transported to the Maswik Lodge Cafeteria on the South Rim, where the American Red Cross is coordinating assistance, NPS wrote. “No injuries have been reported as of the latest available information.”

Nearly all footbridges spanning Bright Angel Creek, a fast-flowing tributary that flows into the Colorado River, have been destroyed. Hikers no longer have access to the area, which includes the historic Phantom Ranch landmark.

As of this writing, the following areas are closed until further notice, with no estimated reopening dates:

• Phantom Ranch
• Bright Angel Campground
• Phantom Ranch Canteen and cabins
• Entire North Kaibba Trail, from the North Kaibab Trail to Phantom Ranch
• Black Bridge and Silver Bridge

The NPS says it may close additional areas as the full extent of the damage becomes known.

“Park staff are continuing to assess damage to trails, bridges, utilities, facilities and other infrastructure,” NPS wrote.

Authorities warn that additional rainfall is expected on August 31, which the NPS says could could result in more flash floods, debris flows, rockfall and changing trail and river conditions.

Hikers and boaters should contact their commercial outfitter or the NPS River Permits Office for more information about any upcoming trips.