Emissions from a shipwreck may have caused the mysterious chemical haze that forced the evacuation of the Sussex coastline and left dozens of holidaymakers with streaming eyes, sore throats and vomiting.
Emergency services warned people on Sunday to keep doors and windows closed after people were affected along the shoreline from Eastbourne to Birling Gap.
Footage showed the haze coming in from the sea like a mist.
After the cloud dissipated, focus turned to what had caused the haze and many explanations were put forward.
On Friday evening, the Maritime and Coastguard Agency issued an update on its investigation, saying a shipwreck was among the avenues it was exploring.
The agency said: "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.
"We have identified approximately 180 vessels that passed through the English Channel off the coast of Eastbourne on Sunday 27th August.
"We are working with all relevant Environmental and Public Health regulators to conclude these investigations. We have no further information at this stage."
The Met Office has already said the haze is unlikely to have come from northern France.
Winds were very light, and blowing in the wrong direction, and the air remained relatively still all day.
Prof. Andrea Sella, at University College London, told HuffPost UK that an emission from a ship was a possible explanation for the haze.
"An alternative could be that a ship may have dispersed something. This is illegal but possible," she said.
"Such a discharge could react again with sunlight, explaining the unpleasant and highly disagreeable symptoms."