The National Park Service is asking for the public’s help finding as many as 20 people who may be missing following a significant flash flood in the Grand Canyon on Saturday.

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“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,” the agency wrote in a new release and social media posts on Sunday afternoon.

This includes people who may have been traveling along the North Kaibab Trail from the trailhead to Phantom Ranch, staying at Bright Angel Campground or traveling or staying in the area known as “the Box” north of Phantom Ranch, officials said.

The park service said the flash flood happened around 2:30 p.m. Saturday and resulted in “significant impacts” to infrastructure throughout Bright Angel Canyon. Nearly all footbridges were destroyed, eliminating hiker access to the creek.

Sixty-two people were evacuated from the area Sunday morning, and additional evacuations were underway from Cottonwood Campground, Phantom Ranch and other nearby sites.

Evacuees have been transported to the Maswik Lodge Cafeteria on the South Rim, where the American Red Cross is coordinating assistance.

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Phantom Ranch, Bright Angel Campground, the Phantom Ranch Canteen and cabins, and the entire North Kaibab Trail from the North Kaibab Trailhead to Phantom Ranch are closed until further notice, the Park Service said.

The Black Bridge and Silver Bridge crossing the Colorado River are also closed until further notice with no estimated reopening date.

A flash flood watch remains in effect in the Grand Canyon area through Monday evening with more showers and thunderstorms in the forecast, according to the National Weather Service.

“Flash flooding will be possible in creeks, normally dry washes, swimming holes, and over recently burned areas,” the agency warned. “Raging killer currents will be possible in side canyons and narrow slot canyons. Low-water crossings may be flooded.”

Anyone with information is asked to contact the National Park Service Investigative Services Branch Tip Line at 888-653-0009 or [email protected].

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