Adults, teens and children as young as two were enjoying a summer afternoon by cooling off in an Arizona creek when the gentle waters turned deadly.

The group from the Phoenix and Flagstaff areas had met Saturday for a day trip along a popular swimming hole near Payson, Ariz., about 161 kilometres northeast of the capital. They set up lounge chairs not knowing an intense thunderstorm was dumping heavy rainfall just upstream in the Tonto National Forest.

'They heard a roar, and it was on top of them.' — Fire Chief Ron Sattelmaier

The storm unleashed nearly two-metres-high floodwaters, dark with ash from a summer wildfire, onto the unsuspecting family and friends. The torrent carried away tree branches and other debris and left a wake of nine bodies.

Search and rescue crews, including people on foot and others in a helicopter, recovered the bodies of five children and four adults, some as far as three kilometres down the river. Authorities did not identify them.

One person — a 27-year-old man — is still missing. Authorities originally said they were looking for a 13-year-old boy, but on Monday morning an official with the Gila County Sheriff's Office said the large number of victims led to a miscommunication among emergency workers. 

The boy's body was found on Sunday, according to Det. David Hornung.

About 40 volunteer search-and-rescue workers and four search dogs resumed the search early Monday.

Clinging to a tree

Disa Alexander was hiking to the swimming area where Ellison Creek and East Verde River converge when the water suddenly surged.

Video she posted to social media showed torrents of water surging through jagged canyons carved in Arizona's signature red rock.

"I could have just died!" Alexander exclaimed on the video.

She spotted a man holding a baby and clinging to a tree. Nearby, his wife was also in a tree. A boy Alexander described as the couple's son was on the rocks above the water.

Had they been swept downstream, they would have been sent over a six-metre waterfall, Alexander said.

Flash Floods Arizona

Search and rescue crews have recovered bodies of children and adults, some as far as three kilometres down the river after Saturday's flash flooding poured over a popular swimming area inside the Tonto National Forest in central Arizona. (Ralph Freso/Associated Press)

Alexander and others tried to reach them but couldn't.

Fortunately help was close by.

Some search and rescue team members were already near the swimming hole after getting a call to help someone who had suffered a bad allergic reaction, according to Hornung.

When they arrived at the scene, "they heard someone screaming for help and saw a man clinging to a rock," said Hornung, who added that the man was safely rescued. "Then they heard other people calling for help."

Four people were rescued and taken to the hospital for treatment of hypothermia.

Flash Floods Arizona

Members of the Tonto Rim Search and Rescue team walk back to the Gila County Sheriff's Office mobile command centre on Sunday. (Ralph Freso/Associated Press)

Rescue crews comb waters

Rescuers in bright orange T-shirts and helmets dotted the green landscape as they combed the waters and banks. 

The family, who was staying in the area, declined to be interviewed when approached by an Associated Press reporter.

The National Weather Service estimated up to 3.8 centimetres of rain fell over the area in an hour. The thunderstorm hit about 13 kilometres upstream along Ellison Creek, which quickly flooded the narrow canyon where the swimmers were.

Hornung noted that the National Weather Service had issued a flash flood warning about one and a half hours before, "but unless they had a weather radio out there, they wouldn't have known about it. There is no cellphone service out here."

The swift waters gushed for about 10 minutes before receding in the narrow canyon, Hornung said.

"They had no warning. They heard a roar, and it was on top of them," Water Wheel Fire and Medical District Fire Chief Ron Sattelmaier said.