The reason why children coughed and struggled to breathe at a packed beach on the hottest late August bank holiday weekend on record in the UK remains a mystery.
Hundreds of families were enjoying the sun in the seaside town of Frinton in Essex on Sunday, when a large number of people began to have trouble breathing.
Essex Police said they were investigating, but that the cause remained unknown and the force advised people not to enter the water.
Emergency services, including the ambulance and fire service, attended the scene at the seafront off Fourth Avenue shortly after 2pm.
Despite speculation of a fuel spill from a ship, the Maritime and Coastguard Agency, which sent a counter surveillance pollution aircraft to the scene, said no evidence of this has been found.
A mother on a family day out at the busy beach described how one of her twin daughters was left “gasping” for breath.
Miriam Lansdell told the PA news agency: “My daughter started coughing. She said ‘I don’t feel good. It hurts to breathe in’. My other daughter was gasping and couldn’t form words because she couldn’t breathe well enough.”
The 45-year-old mental health worker from Derbyshire, who was visiting her parents in Essex for the bank holiday weekend, said she had also had difficulty breathing as she lay on the sand drying off after a dip in the water.
She said they all began to breathe more easily when they moved further away from the beach, but took the 10-year-old girls to a walk-in clinic to be checked over by medical staff.
She added: “It’s not what you expect when you go for a day out to the beach.”
Training manager, Mark Wray, who was at the beach with his wife, said he had noticed a few children coughing as they came out of the sea, but assumed they had swallowed some water.
He said officials later began patrolling the beach and starting to tape off some areas, before “a procession of emergency vehicles, including ambulances, fire appliances, police cars and other unmarked vehicles with blue flashing lights started heading towards the scene”.
He said the beach was “packed with hundreds of families enjoying the record-breaking temperatures”.
Essex Police said that while the cause was investigated, people were advised not to go into the sea.
East of England Ambulance Service said people should wash themselves down if they were in the water, change their clothes and drink fresh water.
Anyone with further concerns is advised to call the NHS on 111.
A spokeswoman for the Maritime and Coastguard Agency said: “At around 2.30pm on Sunday afternoon, HM Coastguard received reports of beach swimmers suffering from a possible respiratory irritant causing people to cough at Frinton and Walton-on-the-Naze on the Essex coast.
“The Maritime and Coastguard Agency (MCA) has not received any reports of pollution being spilled in the area from vessels.
“The MCA’s counter pollution surveillance aircraft has flown over the area this afternoon to undertake an aerial survey and no fuel pollution has been reported by this flight.”
Earlier this month a hazardous material left several people on Worthing seafront complaining of sore eyes and vomiting, and two requiring hospital treatment.
The coastguard said a passing cargo ship might have been the cause.
An investigation was launched in August 2017 when a chemical haze in Eastbourne left 150 people needing hospital treatment for sore eyes and breathing problems.
The most likely cause of that incident was believed