Aug. 30 (UPI) — More than 20 people are missing after “significant” flash flooding struck areas around the Grand Canyon, officials said Sunday.

The National Park Service asked for those who know of hikers or backpackers who were in the Grand Canyon National Park areas of Bright Angel Canyon and Phantom Ranch when the flooding hit to contact park officials.

“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,” NPS said in a statement.

The NPS said it is also searching for anyone who may have been on the North Kaibab Trail from the North Kaibab 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 at least 62 people had been evacuated after significant damage was caused by the flooding.

Phantom Ranch, Bright Angel Campground, Phantom Ranch Canteen, the North Kaibab Trail, the Black and Silver bridges and traffic to the Colorado River in the area are closed “until further notice,” officials said.

A reopening date has not been announced.

Officials warned thunderstorms and heavy rainfall were possible Sunday and Monday that could “result in additional flash flooding, debris flows, rockfall and rapidly changing trail and river conditions.”

People were encouraged to stay away from the closed areas.

Grand Canyon National Park is the country’s fourth-most visited national park, with 4.4 million visits last year.