A man is believed to have died after falling more than 60ft from the top of a waterfall.
The man is believed to have plunged 60ft
Firefighters, ambulance, fell rescue and police were called to the High Force Waterfall, a tourist attraction at Forest In Teesdale, County Durham.
The man was said to have plunged into the River Tees below the waterfall.
Police divers could not join the rescue effort because of the river conditions and submerged ledges at the base of the falls.
A Durham Police spokesman said: "The area was closed and a full search made without success.
"Details of the missing man, believed to be in his 30s from the Jarrow area, are being withheld until his family have been informed.
"It is intended to close the outfall at Cow Green Reservoir. This will reduce the present heavy flow of water over the falls and allow police divers to commence a full search of the base of the falls."
He said access to the area would be restricted during the operation.