The cause of a mystery illness which struck visitors to beaches along a stretch of the Essex coast may never be known, according to officials.

Speculated causes for the sudden and unexplained sickness have included algae, a fuel spillage, and a spike in pollution or ozone levels.

Council chiefs said a range of possibilities had been examined - but that tests remained inconclusive.

No further reports of breathing difficulty or irritation to eyes have been reported in the two days since the sickness swept beaches in Frinton, Clacton and Walton.

Beach goers had been told to avoid the water - and Tending District Council asked the public to still exercise caution around the water.

A spokesman added: "There have been no reported incidents in relation to the seawater over the last two days.

"Our current guidance for the public is to use caution around the water.

"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.

"Incidents such as these are not unheard of around the country's coastline, and often with the tides pass quickly, we have taken precautions until we are satisfied there is no further risk.

"We are still awaiting test results, but we have been advised there is no guarantee these will prove conclusive.

"We are aware of a number of speculated causes, ranging from algae, a fuel spillage and a spike in pollution and ozone levels, and we would reassure the public we have looked into a whole range of possibilities. However, it is possible we will never know for sure what caused this incident."