The coastguard in the UK says a mysterious gas cloud that appeared on the coast of East Sussex in England may have been caused by a shipwreck.

More than 100 people had to be treated for watering eyes, sore throats and nausea following the incident last Sunday.

The unknown haze led to residents being urged to keep their windows closed.

The UK's Maritime and Coastguard Agency is investigating the event.

In their latest statement, the agency explained: "As part of our investigations we are considering a number of possibilities, such as discharges from a vessel, previously unreported lost cargo, and emissions from known shipwrecks."

According to the statement, officials have also identified around 180 vessels that passed through the English Channel off the coast of Eastbourne last Sunday.

Investigators are working with environmental regulators in a bid to identify the cause of the cloud.

Simon Boxall is a senior lecturer in oceanography at the University of Southampton, and suggests there could have been another cause.

He observed: "The ozone levels around Eastbourne peaked quite high just before this toxic cloud came ashore.

"We've seen a lot of plankton growth in the English Channel, and that interacts with ozone to produce a very weak acid."