Rescuers are searching for survivors of a flash flood that tore through campsites in a remote forest in the southern US state of Arkansas, killing at least 18 people and injuring 20 others.
Teams are using helicopters, horses and canoes to scour the mountainous area in the state's south-west.
Rescuers admit they do not know how exactly many people they are looking for. Bodies may have been washed away and the search for the missing could take days if not weeks, the BBC says.
As many as 300 people were believed to be in the area at the time but it was unclear how many were campers and how many local residents, officials say.
Police say campers in the Ouachita mountains were taken unaware by a wall of water bearing down on their campsite in a national park in a remote area of the state's south-west.
A river gauge at Langley, just south of Albert Pike in the Ouachita National Forest, showed that the water rose 2.4 metres in an hour, according to the US Geological Survey.
Some campers have described how they had to cling to trees for hours to survive. The remains of destroyed tents and damaged log cabins were later seen lining the banks of the swollen rivers.
