EXPERTS are investigating a number of ships they think could be responsible for a chemical cloud that spread along the coast leaving more than 150 people needing hospital treatment.

The Maritime and Coastguard Agency (MCA) confirmed that it is continuing to investigate potential offshore sources of the thick yellow cloud that left residents and holidaymakers with skin irritation, streaming eyes and sickness.

Hundreds of people were evacuated from beaches between Eastbourne and Birling Gap after the MCA declared the mist a major incident on Sunday afternoon.

Officials said the mist had cleared on Monday and that it was safe to open windows and doors again.

An MCA spokesman said: “We have never come across anything like this before.

“It did seem to come from the sea, but we don’t know what. Vessels are being looked at. It could be a couple of days or more before results may come back. If there is a source revealed we will let people know.”

A number of residents reported seeing a ship heading towards Shoreham emitting yellow fumes shortly before the mist started to affect people.

A 38-year-old from Shoreham, who asked not to be named, said: “I walked to Southwick beach, near the wind turbines at Shoreham Port, at around 12:45pm on Sunday.

“I noticed a large ship a few miles off the coast in the direction of the Rampion wind farm, but closer to the shore than the wind farm. The ship was emitting an unusually large amount of yellowy-brown exhaust fumes.

“It rose up a short distance and then levelled off, forming a cloud over the ship. It was a hot, still day and the exhaust fumes did not seem to dissipate.”

Graham Howson, 48, from Worthing, tried to call police to tell them he had also seen a dredger heading towards Shoreham Harbour at around 1pm emitting a “gunky yellow fog”.

Others said they had seen a dredger called Sand Heron on the ShipAIS tracking website which had left Southampton the night before mooring up in Shoreham Port at around 2pm on Sunday.

Cemex UK Marine Ltd, owners of Sand Heron, said the ship does not carry any chemicals capable of producing the yellow mist.

Brighton Pavilion MP Caroline Lucas and Eastbourne MP Stephen Lloyd have called for an urgent investigation.

Mr Lloyd MP said: “I want the agencies to identify what it was, how it happened and if there are any long-term dangers.

“Then if an individual or body is found to be responsible, I want them to be prosecuted.”