MORE than 20 people may be missing or unaccounted for following a flash flood in Grand Canyon National Park in Arizona in the US.

The US National Park Service said the “significant flash-flood event” hit the Bright Angel Canyon and Phantom Ranch area on Saturday. 

The statement urged “anyone who knows of hikers or backpackers who were in the inner canyon along the Bright Angel Creek corridor on August 29, as well as anyone who had a campground reservation in the affected corridor, to provide information to the National Park Service Investigative Services Branch.”

Park officials said they are continuing evacuation and response efforts in co-ordination with the Arizona Department of Public Safety, while working to account for individuals who are still not accounted for.

The flash flood caused significant damage to infrastructure throughout Bright Angel Canyon. Nearly all footbridges spanning Bright Angel Creek were destroyed, preventing hikers from crossing the creek, according to park officials.

Officials said parts of Grand Canyon National Park had been closed and the Colorado River was closed to river traffic until further notice.

They also warned that additional thunderstorms and heavy rainfall were possible, potentially causing further flash flooding.