LONDON • Health officials in England say 233 people were treated in hospital after a suspected chemical leak along Britain's southern coast.

Emergency services evacuated a beach in Sussex on Sunday after people at Birling Gap reported pain and a stinging feeling in their eyes, and breathing difficulties when a "mist" appeared.

Sussex police said there was an "unknown haze coming in from the sea". Surrounding roads were closed and the public advised to avoid the area, Xinhua reported.

The Guardian newspaper said one of its reporters, Mr Ian Cobain, had been walking along chalk cliffs known as the Seven Sisters. "At midday, we could see a thick mist off the coast, below the cliffs, but assumed it was just a sea mist. It was immense," he said.

The Telegraph yesterday said early suggestions that the noxious mist had drifted from France had been discounted by the police, who said wind patterns suggested the cloud had not come from the European continent.

Scientists suggested the haze had instead come from shipping in the English Channel or had come from further along the English coast, said the Telegraph.

The coastguard there said it was working with its French counterparts and looking into vessels that were in the area at the time, according to BBC News.

Mr Bob Jefferey of the Royal National Lifeboat Institution Eastbourne Division told the BBC: "Whatever it was, it smelled like burnt plastic. It hung about and didn't move... because there was no wind."

East Sussex Fire and Rescue Service said it was "extremely unlikely" the substance involved was chlorine, added BBC News.

"Beautiful afternoon at Birling Gap cut short by some weird mist, burning everyone's eyes which led to the beach and cliff being evacuated," tweeted Mr Dan Sankey.

"Birling Gap some weird gas leak. People crying," Mr Sameer Jadhav tweeted.

Emergency services yesterday reopened the beaches after all traces of the haze had disappeared.