At least one hiker was killed Monday afternoon when flash floods ripped through slot canyons in Utah’s San Rafael Swell, prompting a massive search by ground and air for other possible victims.

The Emery County Sheriff’s Office said the person died in Little Wildhorse Canyon, a popular hiking destination near Goblin Valley State Park, while 21 others made it out of the flooded canyon safely.

Emery County authorities had dispatched three helicopters as well as ground teams from three neighboring counties to check out slot canyons after heavy rains struck, dropping nickel-sized hail. Search and rescue operations were still underway Monday as night fell.

(Photo courtesy of Emery County Sheriff's Office) Little Wildhorse Canyon in the San Rafael Swell is one of Utah's most popular hikes, but it can be dangerous as the trailhead sign indicates. Flash floods on Monday forced many hikers to run for their lives and claimed at least one victim. Joined by several other agencies, Emery County authorities mounted a massive search for others who may remain stranded in the slot canyons near Goblin Valley State Park.

A news release issued at 7:55 p.m. from the sheriff’s office said there are cars parked at trailheads in the area, leading authorities to believe there are still hikers unaccounted for.

Participating in the search are Emery, Grand, Wayne and Sevier counties, Utah Highway Patrol, the Bureau Land Management, Utah State Parks and Utah Division of Wildlife Resources. Classic Air provided two helicopters and the Department of Public Safety provided a third.

This story will be updated.