Cumbria Great North Swim cancelled over safety fears
Event bosses have been forced to cancel the Great North Swim in Cumbria after blue-green algae was found in the water which could be dangerous.
The Environment Agency found the algae, which could cause sickness or skin rashes, in Windermere.
Nearly 9,000 people signed up for the charity swim which was due to take place this weekend.
Event organisers, Nova International, hope to reschedule the race for later this year.
A spokesman said safety was the top priority: "We are looking at a potential new 2010 date and will let you know by email.
"We realize that the postponement will affect many people, but the safety of all swimmers has to be our number one priority at all times."
Competitors can either take part in the race when a date is announced, accept a full refund of their entry fee, or gain entry into the event next year.
Now in its third year, the swim in Cumbria raises money for charities and provides a boost to the local economy.
In 2009 an estimated 20,000 spectators watched 6,000 swimmers brave the one-mile, open-water course.