Two people have died and 14 remain missing or unaccounted for after flash flooding swept through parts of the Grand Canyon, the National Park Service (NPS) has said.

The flood hit Bright Angel Canyon and the Phantom Ranch area on Saturday afternoon, wiping out footbridges and propelling boulders downstream.

The body of a 46-year-old man was found on Sunday evening near Crystal Rapids along the Colorado River, the park service told CBS News, the BBC’s US partner. Sixty-two people have so far been airlifted out of the area.

“The whole thing was terrifying,” said Nikki Baggs, 41, who was among those to be airlifted out of the bottom of the Grand Canyon with 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 (04:30 GMT).

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 co-ordinated effort,” she said. “That’s what made us feel safe about all of it in an unsafe situation.”

Baggs said she and her friends watched from higher ground as bridges were swept away.

In a statement on Monday, the NPS said search and rescue efforts continue.

The recent rains in the Grand Canyon area, and more widely in south-western parts of the US, are due to monsoonal showers.

A change in wind direction at this time of year pulls warm, moist air northward from the Gulf of California and the tropical Pacific, triggering storms over mountainous terrain.

The storms are difficult to pinpoint in forecasts and so can strike without warning. But because the ground is usually very dry, any heavy downpours lead to dangerous flash flooding and frequent lightning which increases the threat of wildfires.

Flood watches from the National Weather Service cover large parts of Arizona, as well as New Mexico, Utah and Colorado. There are lots of showers currently showing on the weather radar and these downpours will continue during Monday.

The threat of flooding is something that will remain for many more weeks. The North American monsoon season usually runs to the end of September.

Joey Martin told the BBC that he was at the Grand Canyon working on a transcanyon pipeline project when dense, grey clouds rolled in.

He described rain “coming down so hard and so thick that you couldn’t see the Grand Canyon walls”.

“You couldn’t see anything,” Martin said.

Visibility returned roughly 30 minutes later, he said. That’s when he saw the creek begin to rise. It eventually turned into a torrent of mud and debris that slammed into a nearby bridge connecting Martin’s work site to his living quarters.

“From where we were standing, it looked to be about 15ft tall,” he said. “That wall of debris ended up taking out the bridge right there.”

Martin said he and roughly 16 other workers were there and coordinated with NPS once it became clear conditions were unsafe. They gathered hikers in the area and headed for higher ground.

Eventually all were airlifted out.

“It was scary,” he recalled.

“Never been in any kind of vicinity of something like that to that caliber,” he said. “Staying calm was hard, but everybody kind of played a part in keeping people calm and keeping people, you know, focused on just getting away from the danger.”

The NPS initially said it was looking for information about 15 people who were thought to be missing or unaccounted for.

It reported that flooding had caused significant damage in some areas and that trails in the area have been closed.

Overnight guest lodgings in the South Rim will be stopped from Monday until further notice as the floods have caused “extensive damage” to the national park’s water infrastructure.

On Monday, the NPS said that preliminary assessments indicate about 40% of the Transcanyon Waterline, which delivers water for visitors and approximately 2,500 residents, was damaged or destroyed in the flood.

The NPS 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.

The NPS also warned that more thunderstorms and heavy rainfall were forecast for 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. (BBC)