More than 100 ducks who died at a Doncaster park died after eating rotting vegetation which gave off poisonous toxins, tests have revealed.
The lake at Sandall Park has been closed for more than a week after dozens of birds were found dead in the water after being struck down by a mystery virus.
There was speculation that the animals had been killed by water pollution, bird flu and even KFC leftovers and mouldy bread.
But at the same time the source of the outbreak was revealed, park volunteers revealed evidence of mouldy PIZZA being fed to the birds.
Now vets have finally confirmed the source of the poisoning as decaying vegetation at the bottom of the lake - made worse by the heatwave.
Dave Wilkinson, Doncaster Council's Assistant Director for Trading and Property Services, said: “The Animal and Plant Health Agency have now confirmed that the ducks at Sandall Park have died from a toxin that is produced by decaying vegetation at the bottom of the lake, made worse by the hot weather.
"The ducks have been feeding on the rotting vegetation and the toxin is poisoning them.
“We are working closely with the Friends of Sandall Park and the angling club to ensure all dead and sick animals are removed from the lake and the area is safe for all visitors.
"If you do see sick or injured ducks or other wildlife, please contact the RSPCA on 0300 1234 999.”
The alarm was raised last Monday after anglers found the bodies of dozens of ducks floating in the lake.
Signs were erected and visitors warned to stay away from the water while investigations were carried out.
The park has remained open throughout but dog walkers have been told to keep animals away from the lake while people have been told to wash their hands if they come into contact with the ducks.
Visitors have also been told not to feed the ducks bread or mouldy, rotting food and take their rubbish home with them.
The confirmation of the source of the outbreak comes on the same day that park volunteers revealed evidence of pizza being fed to the animals.
Friends of Sandall Park chairman Sandra Crabtree posted a photo of the rotting food alongside the lake in the park and wrote: "This is not helpful.
"Who keeps pizza until it's rotting and mouldy and then feeds it to ducks?
"Who can possibly imagine that ducks and birds want to eat rotting food? Do these people not have dustbins? This was dumped today - despite the obvious problem on the lake."