More than 20 people are thought to be missing or unaccounted for after flash flooding swept through parts of the Grand Canyon.

It hit at around 14:30 local time (22:30 BST) on Saturday in Bright Angel Canyon and Phantom Ranch area, according to the National Park Service (NPS).

Sixty-two people have so far been airlifted out of the area, with more expected to follow. No injuries have been reported.

"The whole thing was terrifying," said Nikki Baggs, 41, who was among those to be airlifted out of the bottom of the Grand Canyon on Saturday alongside her two friends.

"It was a beautiful day and then people were screaming, running," she told the BBC.

Baggs said she and her friends had just dropped off their belongings at a cabin in Phantom Ranch – a remote lodge at the bottom of the Grand Canyon – when they decided to venture out to enjoy the nice day. Before they knew it, a flood of water was sweeping through the area.

As soon as the rain hit, Baggs and her friends headed toward higher ground, where they sat at a picnic table, before rangers yelled to them to run again to a different ledge, where they waited with others for hours before they were evacuated at around 21:30 local time.

Baggs said she and her two friends had been looking forward to a steak dinner at Phantom Ranch – but were now just grateful to be alive thanks to a swift response from park rangers.

"It was a really uniquely coordinated effort," she said. "That's what made us feel safe about all of it in an unsafe situation."

The NPS said flooding had caused significant damage in some areas and that trails in the area have been closed. Baggs said she and her friends watched from higher ground as bridges were swept away.

It asked anyone who knew of hikers or backpackers who were in the inner canyon along the Bright Angel Creek corridor on Saturday to get in touch.

It also warned that more thunderstorms and heavy rainfall were forecast for Sunday and Monday, which could lead to "additional flash flooding, debris flows, rockfall and changing trail and river conditions".

The Grand Canyon is one of the most popular national parks in the US, with about five million people visiting each year. The Bright Angel trail is its most popular hike.