The athletes were competing in the Original Mountain Marathon, a two-day race across rough country in Britain's Lake District, about 300 miles north of London. High winds and heavy rain affected much of northwest England on Saturday.
According to the marathon's Web site, the race was called off just after noon Saturday. It's unknown how many people are stranded in the mountains."It is impossible to say how many people are up there because there is no mobile (phone) reception," said Bob Liddell, a member of a local mountain rescue team. "I don't believe the organizers will have been able to account for everyone at this stage."
Liddell said rescue teams would not be using Royal Air Force search-and-rescue helicopters because of the wind.In a statement, Cumbria Police said about 840 people had taken shelter in four different locations in the area, including a school, farm, and outdoor center.
"The competitors are mainly seasoned mountaineers, and are expected to be carrying suitable equipment to cope with adverse weather," the release said.
The Original Mountain Marathon Web site says the race was founded in 1968. Teams are "totally self-supporting," and competitors do not carry global positioning systems or mobile telephones, the Web site says.
Competitors race in pairs and carry their tents, clothing and enough food for 36 hours.
"The ethos of the event is to be totally self-reliant, in the wilds, carrying all equipment, no outside support," the Web site says.
"The event is for experienced fell (large hill) runners and everyone should have been able to cope," said Shane Ohly, who spoke to the BBC after completing the race. He said that if competitors got into difficulty they should be able to get into their tents to ride out any bad weather.
Mark Weir, who manages a mine in the area, said he had sheltered about 300 athletes.
"The weather is absolutely horrendous and it's a scene of chaos up here," he said.
The sleepmonsters.co.uk Web site, which filed reports on the race, said conditions had deteriorated throughout the afternoon.
"It seems likely many of those retiring will have to spend the night in whatever shelter they can find ... and everyone will have to wait until the rain stops and the waters subside," the Web site said.
None of the race organizers were immediately available for comment.
According to local hospitals and rescue services, more than a dozen people were treated for minor injuries and mild hypothermia.