Dog walkers are being urged to steer clear of a popular lake, after toxic blue-green algae is suspected to have wiped out hundreds of fish.
The Environment Agency said it was investigating reports of around 200 dead fish found at Herrington Country Park in Sunderland.
Environmental officers believe this was caused by a bloom in blue-green algae, which looks like scum appearing on the surface of the water and is common in lakes and ponds during hot weather with less rainfall.
The algae can produce harmful toxins which can be deadly to dogs, reports Chronicle Live.
It has been known to prove fatal to animals just 15 minutes after consumption of contaminated water.
The owner of the property on which the lake sits, Sunderland City Council, has put up signs warning people about the dangers of swimming in the water, urging people and their dogs to stay away.
An Environment Agency spokesperson said the organisation was investigating reports of around 200 dead fish found at the park.
"Blue Green Algae is a naturally occurring environmental phenomenon that becomes more likely during periods of warm, settled, dry weather,” the spokesperson said.
"We ask the public to report any sightings of dead fish or fish in distress to our incident hotline on 0800 80 70 60."
Councillor Claire Rowntree, Deputy Leader of Sunderland City Council, the council's Cabinet Member for environmental matters, and Hetton ward councillor said people should stay away from the lake.
"This blue-green algae poses risks to both public and animal health when it forms blooms and scums in freshwater during warmer summer months,” she said.
"We have posted warning signs about the bloom and the public should please keep themselves and their dogs away from the lake until further notice."
Earlier this year a young dog died while another was left seriously ill after being poisoned by the algae at Scots beauty spot Loch Eck.
The tragic incident prompted Bute and Cowal Vets in Dunoon to issue a warning to owners about keeping their animals away from the water amid rising temperatures, reports the Daily Record .
One dog was brought into the vets seriously ill after suffering symptoms from toxic poisoning.
The animal was given anaesthetic and oxygen while receiving treatment.
Another dog who had been playing in waters at Loch Eck, died shortly after symptoms of poisoning began to show.
