Police have warned of the dangers of swimming in open water after police caught more than one hundred children at reservoirs in Rossendale.
Officers responded to 'numerous reports' of large groups of youths swimming in the reservoirs around Grane Road on Wednesday.
Holden Wood Reservoir, Ogden Reservoir and Calf Hey Reservoir are located just off the main road.
The youngsters were moved from the area, a post on the Rossendale Police Facebook page said.
The Facebook post said: "Today we have received numerous reports of large groups of youths swimming in our reservoirs with in excess of one hundred children being moved from the Grane Road area.
"Reservoirs can be extremely dangerous and we would ask parents to check on the whereabouts of their children today, if they are frequenting reservoir areas please advise them against this to prevent a potential tragedy."
Hordes of people were also pictured at Dovestone Reservoir as people basked in the sunshine on the hottest day of the year.
United Utilities, the water firm in charge of Dovestone Reservoir, Tweeted: "The water in our reservoirs rarely gets above 11°C, even on the hottest of summer days.
"That's cold enough to make you panic. Cold enough to make your arms and legs numb which means you can't swim.
"It can lead to hypothermia, which can cause heart failure and death."
