Up to 50 people have been left with burning eyes and breathing difficulties after a bizarre “chlorine mist” spread across a beach at Beachy Head on England’s south coast.

Emergency services evacuated the popular Birling Gap sun spot in East Sussex after dozens of people complained of sore throats and stinging eyes after the mysterious “mist” appeared on the beach.

@MikeRDrummond chlorine gas has spread in Birling Gap in Sussex. Police & fire brigade have evacuated everyone. Not great scenes. pic.twitter.com/oI22Ot36a3 — A.S.Malik (@kaaptein) August 27, 2017

Numerous witnesses at the scene reported a strong smell of chlorine in the air, but Sussex Police said the source of the “unknown haze” is not yet known.

Sussex Police and East Sussex Fire Service are dealing with an incident in the Birling Gap area. (1/2) — Sussex Police (@sussex_police) August 27, 2017

Thought it was hay fever to start with until we were told to close all windows and doors just now! #BeachyHead and #birlinggap evacuated! — Jonathan Hill (@Jonathan__Hill) August 27, 2017

The haze was first reported just before 5pm Sunday. The coastguard, police and fire and rescue crews are all present at the beach. Emergency services are treating people and clearing the area.

“This seems to have been caused by an unknown haze coming in from the sea, but the source has not yet been established,” the police said in a statement.

Some sort of chemical incident at Birling Gap, eyes are streaming and there's a strong smell of Chlorine in the air pic.twitter.com/rIPMaS58m4 — @Kyle_Crickmore (@Kyle_Crickmore) August 27, 2017

@EastSussexFRS@sussex_police@SECAmbulance dealing with environmental incident nr Birling Gap, many casualties, public advised avoid area — Dawn Whittaker (@CFOESFRS) August 27, 2017

“People living along the coast in the area have been advised to keep doors and windows shut and to move away from the Birling Gap area in particular,” the police added.

Birling Gap some weird gas leak. People crying. Ambulances called. Don't go to Birling Gap at the moment — Sameer Jadhav (@samkoyna) August 27, 2017