Northampton Borough Council has issued a warning to visitors to Delapre Lake after toxic blue-green algae bloomed on the surface of the water.
People have been advised not to enter the water as the algae has a “50/50” chance of being poisonous and the toxins, which can make humans seriously ill and prove deadly for dogs, are undetectable.
According to figures published by the National Water Safety Forum, 44 per cent of people that drowned in 2014 never intended to enter the water, with many of the casualties being runners and walkers.
Councillor Alan Bottwood, Cabinet Member for Environment, said: “Whilst taking a stroll by the river or a dip in a lake may seem harmless, evidence published by expert organisations demonstrates it actually poses some very serious hazards.
“The council is working hard to erect new signage warning of these dangers, and I urge residents to take these hazards into account and to take extra care when around a body of water.”
Instances of blue-green algae blooms can be reported to the Environment Agency via their 24 hour hotline - 0800 80 70 60
If you see someone in difficulty whilst in water, you should phone 999 immediately and ask for the Fire and Rescue Service and Ambulance Service.