A gas cloud that affected hundreds of people along the East Sussex coast appears to have dissipated, police say.

Residents were being urged to keep their windows and doors closed after the unknown haze emerged, but this advice has now been withdrawn.

Holidaymakers were left with streaming eyes, sore throats and nausea – with about 150 people seeking treatment at Eastbourne District General Hospital.

Police are now trying to determine what type of gas caused the irritation, as well as the source of the chemical haze.

It is believed that the gas had been swept in from the sea by onshore breezes – but weather models suggest that an onshore source in northern France is “very unlikely”.

Public Health England is urging anyone who is still suffering the effects of irritation to irrigate their eyes and wash any other agitated areas with plenty of soap and water.

Posts on social media had suggested that the gas involved may have been chlorine, but this has been described as extremely unlikely by the fire service.

Irritation was initially reported by tourists visiting the cliff tops and beach at Birling Gap near Eastbourne just before 5pm on Sunday.

The effects of the haze were also reported as far as Bexhill and towards Hastings.

Mark Battershill, who was one of those affected, told Sky News he was left with stinging eyes and a sore throat after coming into contact with the mystery chemical.

He said some people had complained that they were having difficulty breathing.

Conditions are being monitored at Birling Gap, a popular tourist hotspot, throughout Bank Holiday Monday.