Flash floods swept through campsites in an Arkansas national forest on Friday, killing at least 12 people, police said, as a massive rescue operation was launched in the rugged mountainous area.
Helicopters scoured campgrounds along the Caddo and Little Missouri Rivers in search of survivors after rivers rose by six meters (20 feet) overnight, following heavy rain.
The rivers crested around 5:30 am on Friday, according to officials.
"The preliminary information indicates we have 12 dead," said state police spokesman Bill Sadler. "The primary mission is to get the living out of there that have been trapped."
Officials brought a refrigerated truck to the forest to act as a temporary morgue.
Sadler said it wasn't clear yet whether the dead were locals or visitors to the Ouachita National Forest, which sprawls over 1.8 million acres (700,000 hectares) of western Arkansas and southeastern Oklahoma.
Some 30 people have been rescued so far on Friday, according to the Arkansas Department of Emergency Management, but the rugged and remote terrain and a lack of communications infrastructure is complicating the job.
For one, officials don't know how many campers were in the area because many set up base at scattered sites in the remote hiking area.
"It's not a regular campground where you check in," said Sadler. "We're even having difficulty with our radio communications and moving toward satellite hookups right now. So it will be a while before we have reliable communications in that area."
Arkansas Governor Mike Beebe told CNN it was "a very rapid flash flood that inundated that area" and that there could have been as 300 people in the vicinity, according to the Red Cross.
He said rescue crews "are in the process of trying to determine if there's other people missing and they're in heavy search and rescue mode now with national guard, state police, park and tourism people as well as law enforcement, emergency management personnel."
Beebe said the search was being conducted with helicopters, horses, police cars and trucks and other equipment.