MYSTERY surrounds the cause of a seaside incident which left some beachgoers struggling to breathe after tests returned no definitive results.

Last month more than 150 people were taken ill while enjoying the record-breaking Bank Holiday temperatures, after dips in the sea along the Walton, Frinton to Clacton coastline.

Many of those affected suffered excessive coughing, irritation of the eyes and slight difficulty breathing and were treated by paramedics from the East of England Ambulance Service.

Those with more severe symptoms were taken to hospital and Tendring Council advised beachgoers to avoid entering the water.

A fuel spill was immediately quashed by the Maritime and Coastguard Agency, while the possibility of the issue being caused by an algal bloom was considered feasible.

But test samples of the seawater which were collected from the incident site by the Environment Agency have now found no algal blooms or any unusual or concerning findings.

An Environment Agency spokesman said: “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.”

No further incidents have been reported since the breakout of the invisible cause forced some beaches to close during the 28c heatwave on August 25 and Tendring Council say that are now drawing a line in the sand.

But it has now been revealed that other holidaymakers and local beachgoers positioned further along the coastline also suffered similar problems.

Tendring Council’s communications manager Will Lodge said: “We are pleased the analysis revealed nothing untoward, and the absence of any further reports of similar problems suggests whatever caused the incident has now passed

“We took safety precautions until we were satisfied there was no further risk to the public.

“Incidents such as these are not unheard of around the country’s coastline and we have had reports of others further along the coastline feeling ill on the same day.

“While it is frustrating that 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.”