Sussex Police is advising people that the smell of gas is not a threat to the public.
Shortly after 7.30am on Tuesday, January 22 Sussex Police began to receive calls from members of the public along the East Sussex coast reporting a smell of gas.
Kent Police have also received a larger number of calls.
A Sussex Police spokesperson said: “We understand that this smell emanates from an accidental factory discharge in Rouen, more than 60 miles west of Paris. The smell is from an additive to the gas which has an unpleasant aroma but is not toxic and there is no danger to the public.
“As of 9.15am we had received more than 25 such calls.”
The Health Protection Agency said: “The smell drifting over Southern England today poses no risk to public health. The odour, which is similar to rotten eggs, has been noticed by people mainly in Kent, East and West Sussex and some parts of Surrey.
“It is caused by a particularly smelly chemical that is added to odourless natural gas to give that its characteristic smell.
“The chemical leaked from a factory in Rouen, France yesterday and has blown across the Channel overnight. It is not toxic and has also been diluted before entering the air over England, so people should be reassured it will cause no harm. It is an unpleasant odour which may cause some people to feel slightly nauseous but it will dispel naturally.”
Haywards Heath police tweeted: “Take a look at the link if you detect a smell of gas around Haywards Heath today. Hopefully it won’t Rouen your day.”
People have been commenting on Twitter that they could smell gas over Haywards Heath and Balcombe.