The final sampling of seawater from three Essex beaches has given no indication of what caused a mysterious seaside illness.
On Sunday, August 25 emergency services were called to Walton, Frinton and Clacton seafronts after a large number of people who had been in the water suffered coughing, irritation of the eyes and some minor difficulty breathing.
Tendring District Council (TDC) launched an investigation after beachgoers were struck down with the mysterious illness over the August bank holiday weekend.
Today, they have revealed that nothing unusual was found in the samples, and testing by the Centre for Environment, Fisheries and Aquaculture Science (CEFAs) also revealed no algal blooms in the water.
Will Lodge, communications manager for TDC, said the cause of the incident would remain a mystery.
He added: "We are pleased that the analysis revealed nothing untoward, and the absence of any further reports of similar problems since Sunday, August 25 suggests whatever caused the incident has now passed.
"Incidents such as these are not unheard of around the country's coastline, and often with the tides passing quickly. Anecdotally we have had reports of others further along the coastline feeling ill on the same day, but not reporting it until they saw the media coverage.
"We took safety precautions until we were satisfied there was no further risk to the public. While it is frustrating we are not able to conclusively say what caused this, we are now assured whatever it was is not ongoing, and we can draw a line under this incident."
Tourism bosses had urged visitors to avoid the water at Frinton, Clacton and Walton following the reports of people coughing and struggling to breathe on Sunday, August 25.
Emergency crews, including police and paramedics from the ambulance service, rushed to the seafront that afternoon and more than a dozen people were taken to Colchester General Hospital as a precaution.
Speculated causes for the sudden and unexplained sickness have included algae, a fuel spillage, and a spike in pollution or ozone levels - however TDC are satisfied that there are no further avenues of testing to explore.
An Environmental Agency spokesman added: "We carried out water samples at the relevant sites in a bid to explore what caused the incident. The test results did not identify anything that could have caused the symptoms and our investigation has now concluded."
What should I do if I start to feel unwell?
Should anyone enter the water and experience symptoms such as irritation to eyes or minor difficulty in breathing, they should rinse or wash and change their clothes, and drink fresh water.
If they continue to be concerned or unsure dial 111, the non-emergency health number for advice.
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